The root √KOL served various purposes throughout Tolkien’s life. The root appeared as two separate entries in the Qenya Lexicon of the 1910s: ᴱ√KOLO “to strain through” and also as ᴱ√KOLO, unglossed but with derivatives like ᴱQ. koli- “to prick”, ᴱQ. kolme “point, tip”, and ᴱQ. kolman “peak, summit”, so perhaps meaning something like “✱point” (QL/47). It reappeared in a rejected entry in The Etymologies of the 1930s as ᴹ√KOL with a single derivative ᴹQ. kolma “ring”, and the root had the gloss “round, (?rim)” in an earlier version of the entry (EtyAC/KOL). It had a deleted reference in the entry ᴹ√KOR “round” of which it was probably a variant (EtyAC/KOR).
The root √KOL appeared regularly in Tolkien’s writing in the 1950s and 60s with glosses like “bear, carry” and derivatives of similar meaning (PE17/145, 158; PE22/152, 155; VT39/10). This new meaning of the root was anchored in the words Q. colindo “bearer” as in Q. Cormacolindor “Ring-bearers” (LotR/953), as well as S. coll “cloak” in S. Thingol “Grey-cloak” (PE17/72). In notes from 1969, Tolkien clarified that the root referred “to the ability to support weight or a burden, physical or mental, not necessarily to transporting it” (PE22/155).