Green’s Dictionary of Slang

(N.Z.) despicable.

1971		N. Armfelt Catching Up 124: If I could wring my hands on the bugger who introduced that dog-piss hemlock, I’d wring his neck.
1982		S. King Different Seasons (1995) 476: If you go out alone you’re a hero. Take somebody else with you and you’re dogpiss.