A word appearing as G. corob “a skull” in the Gnomish Lexicon of the 1910s (GL/26), likely related to ᴱ√KORO “be round” (QL/48).

Neo-Sindarin: Since √KOR “round” survived in Tolkien’s later conception of the languages, I’d retain this word as ᴺS. corob “skull”, especially since other early “skull” words such as ᴱN. cas derived from ᴱ√KASA “head” were probably no longer viable since non-initial s generally vanished in Sindarin.