Green’s Dictionary of Slang

hubba hubba! excl.

also hava hava!
[SE hubba! hubba!, a college cheer; according to posting on American Dialect Society List: ‘At one of the WWII training bases in the U.S. there was a sergeant who was known for shouting “A HUB A HUB A HUB” and who was thereby nicknamed Sergeant Hubba Hubba. One day two soldiers were in the town near the base (the author of the account and a friend). They became temporarily separated, when the author of the account spotted two beautiful, charming women walking in his direction. The author wanted to call his friend immediately to take a look at the two women, but he did not want to do so in an obvious and socially gauche manner. So he shouted out something that his friend would understand but would mean nothing to the civilians: HUBBA HUBBA. Later they told the story of this incident about the beautiful women to their buddies back at the base. And HUBBA HUBBA became a local expression on the base in reference to seeing a beautiful woman. A few months later Bob Hope was scheduled to perform at the base, and his advance men (as they always did) visited the base beforehand to pick up anything of local interest that could be used by Bob Hope in his act. They picked up the story about HUBBA HUBBA and gave it to Hope, who did use the expression in his act. That was the seal of approval’]

(orig. US teen/campus) a term of approval, esp. when directed at a passing girl or woman.

[US] AS (1947) XXII 35: The inevitable fact is that the cry ‘Haba-Haba’ is spreading like a scourge through the land.
[NZ]G. Slatter Gun in My Hand 208: She looks right at me. Hubba hubba. That green dress, tight across her bottom.
[NZ]G. Slatter Pagan Game (1969) 175: Mrs Archer, game as Ned Kelly, dancing about wearing nothing but three pot lids. Hubba Hubba.
[US](con. 1942) John Lee Ninth Man 148: One of them winked and mouthed the words, ‘Hubba, hubba,’ but Dietrich ignored her.
[Aus]M. Bail Homesickness (1999) 180: The plane banked and descended and those at the windows turned to each other laughing. ‘Hubba hubba, ding ding!’ Violet cried out.
[UK]Indep. Rev. 6 Nov. 4: And her chest is far from flat / Page-Three Stunna (Hubba hubba).
[UK]Indep. Rev. 26 Jan. 1: He goes, ‘Hubba Hubba!’ He is very provocative and he makes a gesture towards her.
[Aus]L. Redhead Rubdown [ebook] A young Asian woman [...] wearing a black lace slip, stockings, suspenders and high heels. Hubba hubba.