yang yang, n. — Green’s Dictionary of Slang

yang yang n.

[nonsense word + ? play on yang n. on pattern of cock n.⁵ (2)]

(Aus./US campus) nonsense, rubbish; also as adj.

1977		T. Ronan Mighty Men on Horseback 13: He’s got a mob of yang-yang horses, a few moth-eaten packs and saddles and no money.
1989		P. Munro Sl. U. 209: Jake, you talk a lot of yang yang.