Inherited from Proto-Basque *(h)aRi, further derivation unknown. Possibly from Proto-Indo-European *kh₂er- (“hard”), also found in Romance and maybe in Celtic; compare Welsh carreg, Cornish karrek and Middle Irish carrac. However, this hypothetical root is not only attested in Western Europe, but in eastern areas as well, such as in Ancient Greek κάρκαρος (kárkaros), Armenian քար (kʻar, “stone, rock”), Sanskrit खर (khára, “hard, solid”).