Word Origin & History
late 13c., from O.Fr. oncle, from L. avunculus "mother's brother," lit. "little grandfather," dim. of avus "grandfather," from PIE root *awo- "grandfather, adult male relative other than one's father" (cf. Arm. hav "grandfather," Lith. avynas "maternal uncle," O.C.S. uji "uncle," Welsh ewythr "uncle").
Replaced O.E. eam (usually maternal; paternal uncle was fædera), which represents the Gmc. form of the root (cf. Du. oom, O.H.G. oheim "maternal uncle," Ger. Ohm "uncle"). Also from French are Ger., Dan., Swed. onkel. First record of Dutch uncle (and his blunt, stern, benevolent advice) is from 1838; Welsh uncle (1747) was the first cousin of one's parent. To say uncle as a sign of submission in a fight is N.Amer., attested from 1918, of uncertain signification.