possibly from Proto-Uralic. Two different comparisons have been proposed, both with their own problems:
Akin to Proto-Samoyedic *koəjə (“mountain”).
Akin to Proto-Finnic *kaca (“point”), Proto-Samic *keaćē (“point”).
Abondolo (1992)[3] considers the latter comparison "slightly less unconvincing" (and considers hely (“place”) to be the Hungarian cognate to Samoyedic instead). Koivulehto (2001) however has etymologized the Finnic and Samic words for 'point' as early loans from Indo-European, unrelated to Hungarian.

Abondolo, Daniel. 1992. "Locus meliori datus: Hungarian hegy, hős, ős, tőgy, völgy, vas, hegy, hely. — Rédei-Festschrift, pp. 23–28. Wien/Budapest.
Koivulehto, Jorma. 2001. "The Earliest Contacts Between Indo-European and Uralic Speakers." — Christian Carpela, Asko Parpola and Petteri Koskikallio (eds.), Early Contacts between Uralic and Indo-European, pp. 235–263. Suomalais-Ugrilaisen Seuran Toimituksia 242.

Logudorese Sardinian

Wilhelm Meyer-Lübke Romanisches etymologisches Wörterbuch. Heidelberg.