Green’s Dictionary of Slang

1. (US) nonsense.

1946

S. Sterling Where There’s Smoke 36: I suppose you think that’s a lot of hubba-hubba.

2. a lively, energetic spirit.

1940		in Tamony Americanisms (S.F.) No. 7 (1965) 1: Lots of the old hab-hab [...] But spirit alone does not win football games.
1945		M. Berger ‘Army Language’ in AS XX:4 Dec. 262: Hubba-hubba, originally gibberish, now means the spirit of double-time and eagerness.