Green’s Dictionary of Slang

(Aus.) to knock down (fatally).

1919		W.H. Downing Digger Dialect 45: Skittled, killed.
1933		C. Drew ‘Gorilla Grogan’ in Bulletin (Sydney) 26 July 40/2: Banana Harry [...] skittled Basher Murphy in half a round.
1941		A. Gurney Bluey & Curley 6 Oct. [synd. cartoon strip] Stop!! We’ve skittled a bloke!