Green’s Dictionary of Slang

a sexual deviant.

1975		H. Ellison ‘Neon’ in Deathbird Stories (1978) 91: Get offa there, you freako-pervo-devo!
1992		R.G. Barratt ‘Law is a Dope’ in What Do You Reckon (1997) [ebook] Along with the devos, the cops might get sick of chasing the mullheads.
1997		J. Birmingham Tasmanian Babes Fiasco (1998) 69: She sussed that torture boy really was a devo.
2005		B. Hare Urban Grimshaw 56: What you goggling at, devo?