Green’s Dictionary of Slang

a popular, if meaningless, catchphrase.

1853		Dickens ‘Slang’ in Household Words 24 Sept. 74/2: Let some fellow rush forward and roar out ‘It’s all serene,’ or ‘Catch ’em alive, oh!’ (this last is sure to take) pit, boxes, and gallery roar with laughter.
1864		Sherborne Mercury 5 Jan. 3/7: The Catch’em Alive Oh! Joint-Stock Bank [...] Directors Lord Dundreary M.P., A.S.S., Lord Tomnoddy, M.P., A.S.S.