Green’s Dictionary of Slang

1. (mainly N.Z.) a stench.

1941		Baker N.Z. Slang 42: I suspect [...]when we speak of an offensive stench as a ponk we are coupling the Maori puhonga, stinking, offensive, with the earlier English use of pong.
1941		Baker Popular Dict. Aus. Sl. 56: Ponk, a stink.
1958		Willans & Searle Complete Molesworth (1985) 401: No one hav been able to elliminate ponks from labs. They used to be called ‘stinks’.
1988		McGill Dict. of Kiwi Sl. 86/2: ponk stink; possibly from Maori ‘puhonga’, stinking or offensive, and English word ‘pong’, which has the rare form ‘ponk’, also as v., and adj.
2003		McGill Reed Dict. of N.Z. Sl. [as cit. 1988].

2. (US) a smelly, contemptible person.

1972

J. Wambaugh Blue Knight 183: ‘That ponk you tossed in jail that time, ’member?’ [...] ‘Oh yeah, I remember. Sneed was his name. Smelled like dog-shit.’ [...] Ponk-ass bastard,’ said Nate.