cuneus.

Uncertain root, apparently with the suffix -eus. Various problematic comparisons to either Proto-Indo-European *h₂eḱ- (“sharp”) or *ḱúH- (“spike; sting”) (compare Latin culex (“mosquito”), Avestan 𐬯𐬏𐬐𐬁 (sūkā, “needle”), Sanskrit शूक (śūka, “spike; bristle; insect sting”), शूल॑ (śū́la, “spear; stake”) etc.) have been unfruitful; a long vowel (*cūneus) would be expected in the latter case, and the morphology of the -n-eus suffix remains opaque. One possibility is that cuneus is a borrowing from Ancient Greek γώνιος (gṓnios, “corner; angle”) via an Etruscan intermediate which could explain the devoicing, though De Vaan finds this unconvincing. Compare cunnus (“vagina”, derogatory), also of uncertain origin, as well as cutis (“skin”).