ᴹ√I¹ “that (deictic particle); [ᴱ√] here it is, root of relatives”
A root in The Etymologies of the 1930s glossed “that (deictic particle)” (Ety/I¹). A similar root appeared in the Qenya and Gnomish Lexicons of the 1910s glossed “here it is” (QL/41) and “root of relatives” (GL/50). Given Tolkien’s long standing use of i for both “the” and the relative pronouns “that” in all his Elvish languages, this root was established very early and remained more or less fixed throughout Tolkien’s life.
√IBI “*cliff, sheer descent”
A root introduced in 1967 notes to explain Q. imbë “valley”. Tolkien said this word it usually perceived as being related to √IMI “in, within” but then he speculated that “It is possibly from a similar but different stem √IBI, and to be compared with S îf (< *īb-), a cliff, a sheer descent” (PE17/92). A possible precursor to this root was ᴹ√IMBE “dell, deep vale” from The Etymologies of the 1930s which was likewise the basis for ᴹQ. imbe/N. imm of the same meaning (EtyAC/IMBE). Tolkien did not explicitly connect this 1930s root to ᴹ√MĪ/IMI, so it may, like later √IBI, have been of independent origin.
ᴱ√IÐI “dwell‽”
A root in the Qenya and Gnomish Lexicons given as ᴱ√IŘI (QL/43) and iđ- (GL/50), the latter more representative of its true form. In the Qenya Lexicon it was glossed “dwell”, but Tolkien marked this gloss with a “?”. It had derivatives like ᴱQ. indo/G. ind “house”, ᴱQ. irmin/G. Idhru “world”, and ᴱQ. Indi/G. idhrin “men, earth dwellers”. Based on the last of these, a possible precursor to this root is the deleted root ᴱ√(I)LÐ(I)L, also in Qenya Lexicon with the (rejected) derivative ᴱQ. ildi “men” (QL/42).
There are no signs of this root in Tolkien’s later writing, and both “men” and “world” were given new derivations, the latter from √MBAR “dwell”, the likeliest replacement for this root.
√IL “all”
A root meaning “all” in Tolkien’s writings from the 1930s through 1960s (VT48/25) with derivatives in both Quenya and Sindarin, the most notable being Q. Ilúvatar “All-father” (MR/39). Its earliest precursor is the root ᴱ√ILU “ether, the slender airs among the stars” from the Qenya Lexicon of the 1910s, whose derivatives include various sky-words as well as ᴱQ. Ilúvatar, since in this early period the name meant “Heavenly Father” (QL/42). The meaning of the root shifted to ᴹ√IL “all” in The Etymologies of the 1930s (Ety/IL), and it retained this sense thereafter.
ᴱ√ILI¹ “shine oily”
A root in the Qenya Lexicon of the 1910s glossed “shine oily” with derivatives like ᴱQ. ilma/G. ilm “oil” and ᴱQ. ilin (ilim-) “milk” (QL/42; GL/50). The sense “oil” seems to have been transferred to a new primitive form ✶mḷgo in the 1920s (PE13/139). However, ᴱQ. ilin (ilim-) “milk” remains the only Elvish word for “milk”, and I think it is worthwhile to preserve this word by assuming the existence of a Neo-Elarin root ᴺ√ILIM of this meaning. The root ᴱ√ILI might have reemerged in a 1968 note as √LIP “oil” as suggested by Wynne, Smith and Hostetter, but this new root had no derivatives given (VT44/15, 20 note #7).
*√IM “[ᴱ√] same, alike”
A root whose existence is implied in Tolkien’s writings from the 1950s and 60s by various reflexive pronouns such as Q. imni “myself” and S. im “self(same)” (VT47/37). Though the root itself did not appear in Tolkien’s later writings, it seems to have been a long standing idea of his, appearing as ᴱ√IMI¹ “same, alike” in the Qenya Lexicon of the 1910s with derivatives such as ᴱQ. iminqa “exactly alike, identical” and ᴱQ. inye- “imitate, make like” (QL/42). It seems to have had Gnomish derivatives from this period as well, such as G. inco “the same, the identical”, though Tolkien put this form under the root for the definite article: ᴱ√I (GL/50). In any case, √IM as the basis for “sameness” and reflexives seems to have been a well established idea in Tolkien’s languages.
√ING “*highest, top; [ᴹ√] first, foremost”
This primitive element appeared in the Shibboleth of Fëanor written in 1968 in connection to the name Q. Ingwë. The earliest basis for this name seems to be the root ᴱ√INI “tiny, small” from the Qenya Lexicon of the 1910s, from which the name ᴱQ. inwe “one of the royal house of the Eldar” was derived (QL/42); this Inwe was also the earliest form of the name of Ingwe. This name was given a new derivation in The Etymologies of the 1930s from the root ᴹ√ING “first, foremost”, along with the adjective ᴹQ. inga “first” (Ety/ING). The primitive element ing- reappeared in the Shibboleth of Fëanor, again as the basis for Q. Ingwë, which in this document was glossed “Chief” (PM/340). The word Q. inga also reappeared, but with a new gloss “top, highest point”, so the meaning of the root may have shifted from “foremost” to “*highest”.
Thus the conceptual development seems to be 1910s ᴱ√INI “tiny” >> 1930s ᴹ√ING “foremost” >> 1960s √ING “*highest”.
√IN(ID) “mind, (inner) thought, inmost heart, inner senses”
A root appearing in various notes written around 1957 connected to the mind (PE17/145, 155, 189; UT/400; VT43/16). Its most notable derivatives are Q. indo/S. ind “(state of) mind”. In The Etymologies of the 1930s, ᴹQ. indo “heart, mood” and N. ind “inner thought, meaning, heart” were instead derived from the root ᴹ√ID; this 1930s root was unglossed but had derivatives connected to both thoughts and desires, such as ᴹQ. íre “desire, longing” (Ety/ID).
Tolkien introduced a new derivation of indo from √IN(ID) in Quenya Notes written in 1957 (PE17/145, 189):
IN-I-D, mind, inner thought. These refer to the movements or activities of the fëa or “spirit” (rational soul). indo, inner thought, in fea as exhibited in character or [?personality]. indóme, settled character, also used of the “will” of Eru (PE17/189).
The root √IN- “inmost heart, thought, mind” with extended forms √INID and √INIS also appeared in contemporaneous Notes on Names, again as the basis for indo (PE17/155).
Tolkien coined yet another etymology of Q. indo in notes written in 1969, deriving it from √NID “force, press(ure), thrust” (PE22/165). This new derivation doesn’t necessarily invalidate √INID, but rather gives a new basis for the root itself as an vocalic augment of √NID rather than an extended form of √IN-.
√IR “desire, long for; [ᴹ√] desirable, beautiful”
Tolkien experimented with a variety of roots for “desire, desirable”, most in connection to the name Idril. In The Etymologies of the 1930s there was a root ᴹ√ĪR “desirable, beautiful”, but it had no derivatives (EtyAC/ĪR). Elsewhere in the document ᴹQ. íre “desire” was derived from the root ᴹ√ID (Ety/ID), perhaps a new iteration of the (hypothetical) early root *ᴱ√ITI “precious”. This second root ᴹ√ID had various derivatives having to do with both thoughts and desires, such as ᴹQ. indo “heart, mood”, N. ind “inner thought, meaning, heart”, ᴹQ. írima “lovely, desirable”, and N. idhren “pondering, wise, thoughtful”. Among its derivatives Tolkien also gave N. Idhril, untranslated but probably meaning “*Desirable One”.
The problem with this last derivation is that in the contemporaneous narratives, Tolkien generally gave her name as Idril (SM/36, LR/141), which was the form of her name dating all the way in The Lost Tales of the 1910s (LT2/164). When writing the appendices to The Lord of the Rings, Tolkien again used Idril (LotR/1034).
This form of the name could not be derived from √ID, and Tolkien wrestled with this question in his Notes on Names written in 1957 (PE17/112). Acknowledging the problem, Tolkien first considered introducing a new root √IT “(great) enhancement” to serve as the basic of Idril, but he reversed himself, giving √ID “desire, long for” as a better basis for the name, saying: “Decision: [S.] íđril, Q Írilde”. But then he crossed all this through, and considered reintroducing √IT with a modified meaning “repeat, multiply” (PE17/112).
Based on the Shibboleth of Fëanor written 1968, it seems Tolkien stuck with the notion of basing Idril on a √IT, though he revised the meaning of the root again to “glitter” or “sparkle” (PM/363). As for √ID, the meaning “desire” seems to have been transferred back to √IR, which Tolkien gave with the gloss “desire” in notes on roots having to do with “beautiful” written in 1959-60 (PE17/155). Also, around 1957 Tolkien introduced a new root √IN-I-D to serve as the basis for Q. indo “mind” (PE17/155). The various words having to do with “thoughts” derived from 1930s ᴹ√ID may have been transferred to √IN-ID, a possibility suggested by Elaran in a Discord chat on January 26, 2018. If so, Tolkien may have abandon √ID completely.
Assuming the above reasoning is correct, the conceptual development would be 1910s *ᴱ√ITI “precious” >> 1930s ᴹ√IR “desire” >> 1930s ᴹ√ID “desire, thoughts” >> 1957 √ID “desire” >> 1959 √IR “desire”, with thought words transferred to √IN-ID (later √I-NID) and the name Idril transferred to √IT “glitter”.
√IS “know”
The root √IS was the basis for words having to do with “knowledge” for all of Tolkien’s life, as represented by the verb Q. ista- “to know” which likewise retained the same form and meaning for decades. The root first appeared as ᴱ√ISI¹ in the Qenya Lexicon of the 1910s, where somewhat cryptically Tolkien said its Gnomish form was GIS or IS (QL/43). This is mysterious because there were no such Gnomish words beginning with gis- in the contemporaneous Gnomish Lexicon, but there is an Early Noldorin word ᴱN. gist- “to know” from the 1920s, probably derived from ᴱ✶ʒist- (PE13/144, 146); in this early period initial ʒ- > g- in Gnomish (PE12/17).
Tolkien seems to have abandoned this Noldorin variant, giving the root only as ᴹ√IS in The Etymologies of the 1930s (Ety/IS). In this form it continued to appear in Tolkien’s later writings (PE17/155; PE22/129; VT41/6; VT48/25). In one place Tolkien gave the root in inverted form √SI (PE22/134), and such an inversion appeared in some of its derivatives, such as Q. síma “imagination, mind” (VT49/16) and sinte the irregular past tense of Q. ista-. However, the vast majority of its derivatives are from √IS.
√IT “glitter, shine, shimmer, twinkle; repeat, multiply; (great) enhancement”
Tolkien (re)introduced the root √IT in 1957 to address a problem he had with the etymology of the name S. Idril. In The Etymologies of the 1930s, he based this name on the root ᴹ√ID “*desire”, and gave it the form Idhril (Ety/ID). The problem was that in the narratives, he continued to use the form Idril, which could not be derived from √ID. In Notes on Names he wrote in 1957, he introduced the root √IT to provide a new etymology for Idril, giving the root various meanings such as “(great) enhancement”, “gleaming”, “repeat, multiply” and “glitter, shine, shimmer, twinkle” (PE17/112, 156), along with alternate forms ITH, IS and ƷIT (PE17/156). He seems to have settled √IT and the last of the listed meanings, since in the Shibboleth of Fëanor written in 1968 Tolkien said her Quenya name was Q. Itarillë based on ita- “to sparkle”, appearing with various other it- words of similar meaning (PM/346, 348 and 363 note #42).
The root √IT was basically a reversion to the original basis for the name G. Idril, which in the 1910s seems have been based on a (hypothetical) root *ᴱ√ITI meaning something like “precious”. For the effects of these revision on other roots, see the discussion in the entry for √IR “desire”.