Word Origin & History
"aware, up-to-date," first recorded 1908 in "Saturday Evening Post," but said to be underworld slang, of unknown origin. Variously said to have been the name of "a fabulous detective who operated in Cincinnati" or a saloonkeeper in Chicago who "never quite understood what was going on ... (but) thought
he did." Taken up by jazz musicians by 1915; hepcat "addict of swing music" is from 1938.
cry of those leading pogroms or attacks on Jews in Europe, 1839 (but in ref. to the riots of 1819 in Hamburg, etc.), perhaps the cry of a goatherd, or of a hunter urging on dogs, but popularly said to be acronym of L. Hierosolyma Est Perdita "Jerusalem is destroyed."