√YAN¹ “wide, extensive, large, vast, huge; extend”
A root Tolkien introduced in the late 1950s to serve as the basis for various “land” suffixes in Sindarin. The most detailed explanation appeared in a set of documents labeled “Changes affecting Silmarillion nomenclature”:
The endings -ion, -ien, -ian(d) in place names. These have various origins. In Sindarin -ion is usually from -ı̯aun. This in origin is from yānā, √YANA-, extension of yā- (cf. YAGA, gap) “wide, large, extensive”. S iaun “roomy, wide, extensive” … -iand (-ian) is from yandē “a wide region, or country” … This was often used in plural of a single country (especially if it contained a varied topographical apsect) > iend, ien (PE17/42).
Thus all three suffixes -ian(d), -ien(d), -ion originate in the root √YAN. The suffix -ian(d) “land” (Beleriand) is the simplest, just a reduction of ancient -yandē. The suffix -ien(d) “lands” (Anórien) is a plural variant of -ian(d). The suffix -ion (Eregion) is S. iaun “wide, extension” used as a suffix (so perhaps = “*extent”), becoming -ion because of the usual sound change whereby au become o in polysyllables.
In this same document, Tolkien also considered introducing a root √YŎNO “wide, extensive”, going so far as (temporarily) rejected the very well established word Q. yondo “son”. This √YON was blended with √YOD “fence, enclose”, and served as the basis for the suffix -ion, but Tolkien ultimately marked these notes with an “X” to reject them, perhaps because they only explained the suffix -ion, whereas √YAN could explain all three suffixes.
√YAN was mentioned in passing in other documents from this period, variously glossed “vast, huge” (PE17/99), “wide” (PE17/115), and “extend” (PE17/155), and in one place given a variant √YAD (PE17/115). In notes from December 1959 (D59) √YAN was contrasted with √ƷAN, the former meaning “wide” and the latter meaning “long”, both with the basic sense “extend” (PE17/115); see the entry on √HAN for further discussion.
√YAN² “*join”; ᴹ√YAT “join”
The earliest iteration of this root was ᴱ√ẎATA “join” in the Qenya Lexicon of the 1910s with derivatives like ᴱQ. yarta “yoke” and ᴱQ. yatta “neck; isthmus” (QL/105). In the contemporaneous Gnomish Lexicon it had derivatives like G. gada- “join, connect, unite” and G. gath⁽¹⁾ “neck” < ᴱ✶yatt- (GL/36). It reappeared as ᴹ√YAT “join” in The Etymologies of the 1930s with derivatives like ᴹQ. yanta²/N. iant “yoke” and ᴹQ. yanwe/N. ianw “bridge” < ᴹ✶yatmā (Ety/YAT). Above ᴹ√YAT there was a deleted root ᴹ√YATH with a single derivative ᴹQ. yatta “neck, isthmus” that was not deleted (EtyAC/YAK). ᴹQ. yatta may have been transferred to ᴹ√YAT, though as pointed out by Carl Hostetter and Patrick Wynne it might also have been transferred to ᴹ√YAK, which included among its derivatives ᴹQ. yat (yaht-) “neck” (Ety/YAK).
In later writings, Q. yanta and S. iant were used for “bridge” (LotR/1123; SD/129). The word Q. yanwë reappeared with the gloss “joining” in notes from 1969, initially derived from ✶yadme but this was deleted and replaced by √YAN (VT49/45-56). Carl Hostetter suggested that rejected ✶yadme probably reflected the earlier phonological developments seen in The Etymologies whereby tm became dm, then nm, and ultimately nw. However, sometime in the late 1950s or early 1960s Tolkien abandoned tm > dm > nm > nw, deciding instead that tm > tw, which may have motivated him to change the root ᴹ√YAT to √YAN. A similar revision can be seen in change of ᴹ√TEK to √TEÑ in the derivation of Q. tengwa “letter”.
Neo-Eldarin: For purposes of Neo-Eldarin, I prefer to retain the phonological developments of the 1930s to 1950s whereby km, tm > gm, dm > ñm, nm > ngw, nw. As such, I think it is better to retain the 1930s form of the root ᴹ√YAT “join”, which also helps avoid conflict with √YAN¹ “wide, extensive, large”. As the above discussion indicates, Tolkien seems to have been vacillating on tm > tw vs. tm > nw as late as 1969.
*√YAR “dog; *growl, snarl”
In the Qenya Lexicon of the 1910s, Tolkien gave the root ᴱ√YAPA “snarl, snap, bark ill-temperedly” (QL/105). It had no derivatives in QL, but in the contemporaneous Gnomish Lexicon the words G. gab- “bark, bay (of dogs)” and G. gôbi “a large hound” were clearly related (GL/36). There were no similar forms for many years, but then primitive ✶yarr- “dog” appeared in notes from 1968 (VT47/36). This later primitive was likely related to Q. yarra- “growl, snarl” from the Q. Markirya poem of this same period (MC/223), perhaps from a root *√YAR.
ᴹ√YAY “mock”
A root in The Etymologies of the 1930s glossed “mock” with derivatives like ᴹQ. yaiwe/N. iaew “mocking, scorn” (Ety/YAY). Primitive ᴱ✶peia “scorn” from Early Noldorin Word-lists of the 1920s is a possible precursor; its primitive form is very different, but its Early Noldorin derivative ᴱN. hai is not that dissimilar (PE13/146).
*ᴱ√YAYA “steel”
A root implied by the primitive form {ᴱ✶ı̯aksa >>} ᴱ✶ı̯aisa in the Gnomish Lexicon of the 1910s that was the basis for derivatives like G. gais/ᴱQ. yaisa “steel” and similar words (GL/37); in the contemporaneous Quenya Lexicon, the word was ᴱQ. Y̯akse “steel”, consistent with the deleted form in GL (QL/105). In the Early Qenya Grammar and English-Qenya Dictionary of the 1920s, the Qenya word was ᴱQ. akse “steel” (PE14/48, 81; PE15/77). I think it is worth positing a Neo-Root √GAK “steel” to salvage these early words.