The ordinary Quenya word for “twelve”, whose use dates back to at least the Early Qenya Grammar (EQG) of the 1920s (PE14/49, 82). In notes on Eldarin Hands, Fingers and Numerals (HFN) from 1968, Tolkien said its primitive form ✶yūnekē was an elaboration of √ENEK “six” meaning “two (or both) sixes” (VT47/41; VT48/9-10). In Quenya it then picked up a w so that k > kw, either under the influence of minquë “eleven” (VT48/7) or from dual we (VT48/10). Compare also suffixal [ᴹQ.] -rasta “twelve” in duodecimal counting words like yurasta “twenty four” = “✱two twelves”.
Quenya
yunquë
cardinal. twelve
yunquë
cardinal. twelve
enquë
cardinal. six
The Quenya word for “six” derived from the root √ENEK of the same meaning (PE17/95; VT48/7-10; Ety/ÉNEK). The modification of ancient ✱enek- to ✱enekwē was a Quenya-only innovation, influenced by minquë “eleven” and yunquë “twelve” (VT48/7).
Conceptual Development: The word ᴱQ. enqe “six” dates all the way back to the Early Qenya Grammar (EQG) of the 1920s, but there it had a variant enekse (PE14/49, 82). The Qenya Lexicon of the 1910s had ᴱQ. ende “six” under the early root ᴱ√ENE of the same meaning (QL/35).
enquë
cardinal. six
enquë ("q") cardinal "six" (ÉNEK, VT48:4, 6, 9, VT49:57); enquëa ordinal "sixth" (VT42:25); see also enquië. According to VT48:8, the word for "six" may have been encë ("k") in very early Quenya (the form is asterisked by Tolkien), but this was altered to enquë under the influence of yunquë "twelve" (perceived as meaning "2 times 6", *yú-enquë, with the prefix yú- "twi-").
yuncë
cardinal. twelve
yuncë ("k") cardinal "twelve", before it was altered to yunquë under the influence of minquë "eleven" (according to VT48:7, 8). The form yuncë is asterisked by Tolkien. Compare encë under enquë.
rasta
cardinal. twelve
#rasta cardinal "twelve" (isolated from yurasta_ "24", two times 12; cf. the stem RÁSAT "twelve" listed in the Etymologies). See yunquë. (PE14:17)_
yurasta
cardinal. twelve
yurasta cardinal "24" (two times #rasta "twelve") (PE14:17)
yunquë ("q") cardinal "twelve" (VT47:41, VT48:4, 6, 9; VT49:57; also compare the stem yunuk(w)-_ cited in VT42:24, 31). This word appears already in an early source (PE14:82)_. Some sources point to #rasta, q.v., as another word for "twelve". However, available post-LotR sources indicate that Tolkien intended yunquë as the regular Quenya word for "twelve".