The Quenya word for “foot” derived from the root √TAL of similar meaning (PE19/103; VT49/17; Ety/TAL). Given its Sindarin cognate S. tâl (not ✱✱taul) its ancient stem form must have had a short vowel, with the long vowel in the uninflected form the result of the subjective noun case which lengthened the base vowel of monosyllables (PE21/76). Q. tál could also refer to the bottom of things (PE21/21, 76) analogous to English “foot of the mountain” and similar phrases.
Conceptual Development: The earliest iteration of this word was ᴱQ. tala “foot” in the Qenya Lexicon of the 1910s under the early root ᴱ√TALA “support” (QL/88), a form also appearing in the contemporaneous Poetic and Mythological Words of Eldarissa (PME/88). In the Early Qenya Grammar of the 1920s it became ᴱQ. tál with plural tăli indicating an ancient short vowel (PE14/43, 76). In the Declension of Nouns from the early 1930s, ᴹQ. tāl had inflected forms with tal-, again indicating a short vowel in the stem (PE21/21), and likewise with the (1930s-style) genitive form talen in The Etymologies written around 1937 (Ety/TAL). Most of its later appearances also imply a short vowel in the stem, the main exception being the plural form táli in the 1950s version of the Nieninquë “poem”.
tál (tal-, as in "g.sg. talen"; in LotR-style Quenya this is rather the dative singular) noun "foot" (TAL, VT49:17). Also tala (VT49:42). Pl. táli "feet" (PE16:96); here Tolkien did not use tal- with a short a as the stem-form. VT43:16 mentions "an unpublished declension" of this word dating from ca. 1967; here the locative is said to appear as talassë and talsë. Cf. also talya "his foot"; see -ya #4. Early "Qenya" forms:tala "foot" (LT2:347) and dual talwi "the feet" (LT2:347); tálin "feet" (MC:216); instrumental talainen, talalínen (MC:213, 216, 220; this is "Qenya")