avunculus

By surface analysis, avus +‎ -unculus. Actually from an n-stem noun suffixed with -culus, from Proto-Indo-European *h₂ewh₂-on-, a dialectal diminutive of *h₂éwh₂ō (“grandfather, adult male relative other than one’s father”) (whence also Proto-Celtic *awontīr (“uncle”)^[1][2] and possibly Proto-Germanic *awô (“grandfather”), from *h₂éwh₂os (“older male relative”)), whence also avus (“grandfather”).

• (Classical Latin) IPA^(key): /aˈu̯un.ku.lus/, [äˈu̯ʊŋkʊɫ̪ʊs̠]
• (modern Italianate Ecclesiastical) IPA^(key): /aˈvun.ku.lus/, [äˈvuŋkulus]

avunculus m (genitive avunculī); second declension

1. maternal uncle, mother's brother
2. mother's sister's husband
3. great-uncle

Second-declension noun.

• ALF: Atlas Linguistique de la France^[1] [Linguistic Atlas of France] – map 941: “oncle” – on lig-tdcge.imag.fr
• “avoncle” in Diccionari català-valencià-balear, Antoni Maria Alcover and Francesc de Borja Moll, 1962.
• Walther von Wartburg (1928–2002) “avunculus”, in Französisches Etymologisches Wörterbuch, volumes 25: Refonte Apaideutos–Azymus, page 1252

• “avunculus”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
• “avunculus”, in Charlton T. Lewis (1891) An Elementary Latin Dictionary, New York: Harper & Brothers
• avunculus in Charles du Fresne du Cange’s Glossarium Mediæ et Infimæ Latinitatis (augmented edition with additions by D. P. Carpenterius, Adelungius and others, edited by Léopold Favre, 1883–1887)
• avunculus in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette.