This root was established as the basis for “four” very early, though the earliest known Elvish word for “four” was actually ᴱQ. nelde from the Qenya Lexicon of the 1910s (QL/65), which became “three” later on (PE14/49). In the Gnomish Lexicon written soon after, the Gnomish word for “four” was G. cant (GL/25), and by the Early Qenya Grammar of the 1920s, the Qenya word likewise became ᴱQ. kanta “four” (PE14/49, 82). The Quenya word kept this form thereafter, and the Noldorin form became N. canad in The Etymologies of the 1930s, where the root ᴹ√KANAT “four” explicitly appeared for the first time (Ety/KÁNAT). The words and root for “four” remained the same thereafter (VT42/24-26; VT47/15-16; VT48/10), with occasional minor (and transient) variations such as √KENET (VT47/41).
Primitive elvish
ken
root. see, perceive, note, see, perceive, note, [ᴹ√] look at, observe, direct gaze
kenásĭta
adverb. if it be so, may be, perhaps
kemen
noun. earth
kanat
root. four
kanatā
cardinal. four
keme
noun. earth
stīrē
noun. face
stir Reconstructed
root. face
The root ✱√STIR is implied by the names Elestirnë “Star-brow” (UT/184) and Carnistir “Red-face” (PM/353), as well as the primitive word ✶stīrē “face” (VT41/10). It is probably an s-fortification of the root TIR “watch”. It likely replaces the root ᴹ√THĒ “look (see or seem)” from The Etymologies of the 1930s with derivatives like N. thio “to seem” and N. thîr “look, face, expression, countenance”, the latter providing an earlier etymology for N. Cranthir “Ruddy-face” (Ety/THĒ). The original gloss of this 1930s root was “perceive, see” (EtyAC/THĒ). This deleted gloss in turn indicates that 1930s ᴹ√THĒ was itself a later iteration of 1910s ᴱ√SEHE [þeχe] from the Qenya Lexicon, which was mostly connected to eye-words but also had derivatives like ᴱQ. sehta-/G. thê- “see” (PE12/21; QL/82; GL/72); see the entry √KHEN for the later derivation of eye-words.
Tolkien first introduced this root in The Etymologies of the 1930s as a variant of ᴹ√KHEN “look at, see, observe, direct gaze” along with ᴹ√KYEN (EtyAC/KHEN). In The Etymologies it had no derivatives, but in the Quenya Verbal System it appeared with the gloss “see, perceive” as the basis for the verb ᴹQ. ken- of the same meaning (PE22/103). √KEN “see, perceive” appeared regularly in Tolkien’s writing thereafter (PE17/156, 187; PE22/155; VT41/5).