atavism (n.)youdaoicibaDictYouDict[atavism 词源字典]
1833, from French atavisme, attested by 1820s, 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).[atavism etymology, atavism origin, 英语词源]