A word for “thumb” in notes on Eldarin Hands, Fingers and Numerals from 1968 (VT47/10; VT48/5). In rough drafts of these notes it was glossed “picker” as a derivative of √NAP “pick up” (VT47/29). Its (fossilized?) dual form nápat was used to refer to the “thumb and index [finger] as a pair” (VT48/5). Presumably the ordinary dual for a pair of thumbs was ✱nápot or ✱nápu (I personally prefer ✱nápu as a bit more distinctive).
Conceptual Development: In rough drafts of these notes, Tolkien explored several alternate words for “thumb”: Q. tolle, Q. toltil, {(tal)tolle >>} (lep)tolle and tolpe (< ✱tol-lepe), all based on the root √TOL “stick up” (VT47/26-28). In the Qenya Lexicon of the 1910s it was ᴱQ. tyúte “thumb” from the early root ᴱ√TYU whose derivatives had to do with “thick” things (QL/50).
nápo noun "thumb" (VT47:10, VT48:4, 5). Compare nápat.