A noun for “pine-tree” derived from the root ᴹ√THON, also appearing in its genitive plural form thonion “of pines” (Ety/THŌN, EtyAC/THŌN). Helge Fauskanger suggested that it developed from primitive *✶thon- with a short ŏ because the [ō] did not become [ū] before the nasal (AL-Ilkorin/thôn), and only later did the short vowel lengthen in the monosyllable. I think that Mr. Fauskanger may have over-generalized this rule, however, since the other examples of [ō] becoming [ū] occur only before [m] and the change may not have applied to nasals in general. If this is the case, this word could have developed from primitive *✶thōn-. There is not enough evidence to say for certain either way.

Conceptual Development: In notes elsewhere this word was given the form Dor. than with genitive plural form thanion (LR/405), probably associated with the earlier name Dorthanion versus later Dorthonion (LR/145). It is also possible these are Doriathrin and Ilkorin variations of the same word.