Green’s Dictionary of Slang

boo n.7

(US) anything.

[US]Teachers & Writers Collab. Sweet Illusions 28: [W]e’re drinking and talking and Jennifer’s not saying boo.
[US]C. Hiaasen Strip Tease 133: I don’t want to hear boo about it.
[Aus]G. Disher Crosskill [ebook] ‘You won’t hear boo out of them’.