Green’s Dictionary of Slang

1. (Aus.) praise, support.

1900

Bulletin (Sydney) 31 Mar. 10/2: In its own small way the bubonic affair has a lot to recommend it. And yet among all the thousands who cheered for the war there isn’t one to give the plague a well-deserved whoop-up.

2. a plan, a scheme.

1955

‘Blackie’ Audett Rap Sheet 202: That there was the whoop-up, and not a word of it leaked to any place it shouldn’t.