Green’s Dictionary of Slang

double-O n.2

[double-O v. (2)]

(US Und.) an act of betrayal.

[US]C. Coe Hooch! 145: I guess you guys know what it is to get the double-o, don’t you? [Ibid.] 241: I’m tippin’ you off that Paddy Flenger is slippin’ the double-o on you.
[US]J. Tully Bruiser 44: He put the double-o on me.