√KAM root. “fit, suit, agree, be agreeable”
The root √KAM had several distinct meanings over Tolkien’s lifetime. The first appearance of this root is as ᴱ√KAMA¹ “lie down” in the Qenya Lexicon of the 1910s, with derivatives like ᴱQ. kama- “to lie down; (c. loc.) to endure, suffer” and ᴱQ. kamba “bed” (QL/44). Its Gnomish equivalents G. cum- “lie (down)” and G. cumli “couch” hint at a vowel shift (GL/27). In any cases, the sense “lie” was primarily assigned to the root √KAY in later writings, as indicated by the later word ᴹQ. kaima for “bed” (Ety/KAY).
There is another unglossed early root ᴱ√KAMA² from the Qenya Lexicon whose derivatives are mostly different types of red flowers, but there are no signs of √KAM being used for this purpose in Tolkien’s later writing.
The next published appearance of ᴹ√KAM was in the 1930s with the gloss “bind, join” to serve as the basis for ᴹQ. okamna “diphthong” (VT44/13), which replaced (o)samna “diphthong” (< ᴹ√SAM) from The Etymologies, only to be replaced again in the 1960s by Q. ohlon (VT39/9; VT48/29). Thus the meaning “bind, join” for √KAM may have been abandoned as well.
The final published appearances of √KAM as a root were in various etymological notes from the late 1960s. In a couple notes it appeared with glosses “fit, suit, agree” and “suit, fit, be agreeable” and a derived (probably primitive) verb ✶kamta- “to (make) fit, suit, accomodate, adapt” (VT44/14). In notes associated with hands and finger written in 1968, Tolkien proposed √KAM as a replacement for √KAB “hold, contain, retain” from which the words Q. camba/S. cam “(cupped) hand” were derived (VT47/20). It also had a derived verb form camnelyes “you received it” (*cam- “receive”), with nasal-suffixed past form camne- (VT47/21). The verb form was replaced by cambelyes, which might indicate a restoration of √KAB with nasal-infixed past form cambe- (*cav- “receive”), as suggested by Patrick Wynne.
Neo-Eldarin: For purposes of Neo-Eldarin, I think it best to assume that √KAM as a replacement for √KAB was a transient idea, allowing us to use √KAM with the sense “fit, suit, agree” instead.
References ✧ VT44/14; VT47/20
ᴹ√KAM root. “bind, join”
Reference ✧ VT44/13 ✧ kam “bind, join”