Words related to uncle
1833, in biology, "reversion by influence of heredity to ancestral characteristics, resemblance of a given organism to some remote ancestor, return to an early or original type," from French atavisme, attested by 1820s, said to have been coined by French botanist Antoine-Nicolas Duchesne, from Latin atavus "ancestor, forefather," from at- perhaps here meaning "beyond" + avus "grandfather," from PIE *awo- "adult male relative other than the father" (see uncle).
"of or pertaining to an uncle," 1789, from Latin avunculus "maternal uncle," diminutive of avus (see uncle) + -ar. Used humorously for "of a pawnbroker" (uncle was slang for "pawnbroker" from c. 1600 through 19c.).
Being in genteel society, we would not, of course, hint that any one of our readers can remember so very low and humiliating a thing as the first visit to "my Uncle"—the first pawnbroker. We have been assured though, by those whose necessities have sometimes compelled them to resort, for assistance, to their avuncular relation, that the first visit—the primary pawning—can never be forgotten. [Household Words, May 15, 1852]
The extension of the sense to corresponding relationships of descent, "a generation younger than" (grandson, granddaughter) is from Elizabethan times. The inherited PIE root, *nepot- "grandchild" (see nephew) has shifted to "nephew; niece" in English and other languages (Spanish nieto, nieta). Old English used suna sunu ("son's son"), dohtor sunu ("son's daughter").