Green’s Dictionary of Slang

(Aus./US) a nameless object or individual.

1968		G. Slatter Pagan Game (1969) 150: I’ve just about had this cobber thingo.
1972		A. Chipper Aussie Swearers Guide 56: You just refer to him or her as ‘thingo here’ and watch the flush climb to cheeks and neck.
1992		K. Lette Llama Parlour 146: She wants us to go to this charity thingo.
1993		Dly News (NY) Coast to Coast 24 Dec. 23/3: [headline] Ringo’s Thing-O.
2007		Rutland Dly Herald (VT) 27 Dec. 16/6: The gore factor goes up, the Predator goes thingo-a-thingo with various Aliens.