Green’s Dictionary of Slang

1. body odour; thus b.o. juice.

1931		Our Army (US) Feb. 43: Lifebuoy defeats ‘B.O.’ (Body Odor) in any climate.
c.1939		B. Bennett ‘Doctor Goosegrease’ in Billy Bennett’s Third Budget 15: It’ll shift housemaid’s knees, B.O., or D.T.’s.
1948		Dan Burley ‘Back Door Stuff’ 20 Nov. [synd. col.] You smell garlic and whiskey and perfume and onions and a lot of B.O.
1953		Mad mag. Jan.–Feb. 6: His M.O. shows he’s definitely got B.O.
1968		P. Terson Apprentices (1970) I i: B.O. Can you tell your best friend. You could start with Mabel, could you? I mean her B.O. isn’t as bad as the other stuff.
1978		L. Kramer Faggots 29: How could he have made love with another human being and not remember? The face? The body? Something? Anything? A wart? A smell? B.O.?
1982		(con. 1970s) P. Bailey An Eng. Madam 111: Less than 100 years ago [...] it was considered perfectly normal for ladies to smell of ‘B.O.’ under their arms.
1983		J. Byrell (con. 1959) Up the Cross 19: At no time [...] was even the slightest mention made about Whiffy Maloney’ b.o.
1989		H. Rawson Dict. of Invective (1991) 374: The ‘odor’ in the advertiser’s B.O., or body odor.
1992		K. Lette Llama Parlour 155: Seated next to the talkative insul-batt-salesman with B.O.
1998		P. McCabe Breakfast on Pluto 61: There was a distinct whiff of BO emanating from the regions of my armpits.
2000		Observer Rev. 9 Jan. 6: There’s a very strong smell of BO in here! [...] Someone hasn’t used their deodorant today.
2006		G. Malkani Londonstani (2007) 166: His bad B.O. suddenly wiping out the smell a Sanjay’s aftershave.

2. (US) box office.

1936		Ted Yates This Is New York 3 Apr. [synd. col.] Jimmie Lunceford [...] is b.o. hit at the Apollo [...] [Fats] Waller was recently a b.o. hit at Loew’s State.
1944		Advertising & Selling 37 1-6 41/2: She has made Cosmo boffo b.o.