How Well Do You Know English Slang?
late 12c., from Old French lion "lion," figuratively "hero," from Latin leonem (nominative leo) "lion; the constellation leo," from Greek leon (genitive leontos), from a non-Indo-European language, perhaps Semitic (cf. Hebrew labhi "lion," plural lebaim; Egyptian labai, lawai "lioness").
A general Germanic borrowing from Latin (cf. Old English leo, Anglian lea; Old Frisian lawa; Middle Dutch leuwe, Dutch leeuw; Old High German lewo, German Löwe); it is found in most European languages, often via Germanic (cf. Old Church Slavonic livu, Polish lew, Czech lev, Old Irish leon, Welsh llew). Used figuratively from c.1200 in an approving sense, "one who is fiercely brave," and a disapproving one, "tyrannical leader, greedy devourer." Lion's share "the greatest portion" is attested from 1701.