Another exploration of words, this time “letter, line, write”. This is a bit different from my previous examinations, since the most of the words in question are not in dispute, but their etymologies underwent quite a few changes.
The Eldarin words for “letter” are Q. tengwa and S. têw (WJ/396, PE17/44). Tolkien occasionally considered using S. tîw instead (PE22/149, Ety/TEK), but têw is by for the most frequent form, with tîw being reserved for the plural, most notably in the Moria Gate inscription: Celebrimbor o Eregion teithant i thiw hin.
In the Etymologies of the 1930s, ᴹQ. tengwa was derived from the root TEK “make a mark, write” from primitive tekmā. This derivation relied on the phonology change whereby a voiceless stop were first voiced and became nasalized before nasals (PE19/43), so that tekmā > tegmā > teñma > tengwa (PE19/43), a development that surviving into Tolkien’s later writings (PE17/43).
But at some point in the 1950s, Tolkien decided to change the phonetic development of voiceless stops before nasals, so that the nasal was unvoiced instead (PE17/44, PE19/85). The result was that primitive tm became tw in Quenya, not ngw, and TEK could no longer be the root for tengwa. As part of revising the etymology of tengwa and têw, Tolkien shuffled various forms and meanings between several associated roots.
In the original scenario of the Etymologies, the roots for “line” and “write” were TEÑ (<< TEƷ) and TEK respectively. In addition to “letter”, the derivatives of TEK included the words for “pen” (ᴹQ. tekil, N. tegol) the verb for “write” (ᴹQ. tek-, N. teitha-) and the word for a diacritic mark (ᴹQ. tehta, N. teith). The derivatives of TEÑ included the words for “line” (ᴹQ. tie, N. tê), “straight” (ᴹQ. téra, N. taer or tîr) and “row” (ᴹQ. téma, N. tî). Interestingly, the Noldorin word for “alphabet” was derived from a combination of both roots: tiwdi = tîw + tî = “letters row”.
In the 1950s, Tolkien needed a new etymology for tengwa, but couldn’t simply revise TEK, because some of its other derivatives had already appeared in LotR, notably S. teitha- “write”, from the Moria Gate inscription as noted above. Instead, he revised the meaning of the root TEÑ to be “show, indicate, signify” (PE17/44, WJ/394). This new root became the basis for “letter”, with a primitive form of teñmā or tenwā. It also had some new derivatives such as Q. tëa- “indicate” (VT39/6) and Q. tenna “thought, notion, idea” (PE19/97).
[Note that Tolkien also briefly considered using TEW (PE17/44), but since the other later derivatives given above could not come from this root, it seems to have been a transient idea.]
The revised definition for TEÑ meant it could no longer be the basis for words related to “line”. Tolkien seems to have devised yet another new root for these words: TEG (PE19/97). Tolkien only gave explicit derivations for Q. tie “line” and téma row, but all the other derivatives appearing in the Etymologies for TEÑ “line” can be transferred to this new root.
Thus, between the 1930s and 1950s, Tolkien went from two roots (TEK and TEÑ) to three (TEK, TEÑ and TEG), with TEK (“write”) being essentially unchanged except that N. teith >> S. taith, with TEG adopting the meaning of TEÑ (“line”), and with TEÑ being assigned a new meaning (“indicate”).
Note that there is another later root TAN which means “indicate, show”, that is the basis for the names Q. Tannacolli and S. Tengyl “Signifier” (MR/385). It is an elaboration on the demonstrative root TA (PE18/84, 95) and has some conflicting derivatives: Q. tanna “sign, token” and Q. tana- “to show, indicate”. I am not sure whether this use of TAN should co-exist with TEÑ “indicate”.