Green’s Dictionary of Slang

1. a staggering blow; a knockout punch.

1900		Sydney Sportsman (Surry Hills, NSW) 3 Oct. 1/1: Get in a ‘woodener’ that will make hisa big head feel [...] small.
1901		Bulletin (Sydney) 5 Jan. 14/1: ‘You’re a bit knocked about,’ said the doctor, sympathisingly. ‘I believe I am,’ admitted the beery hero of the parching desert; ‘but I reckon I gave the bloke that rushed me a fair woodener!’.
1904		Sun. Times (Perth) 1 May 10/6: Giving the unsuspecting night wayfarer a woodener on the jaw.
1910		Bulletin (Sydney) 27 Oct. 13/2: I told her that if the old blighter had put his nose round the door I’d have given him a woodener, and then raced for safety over his corpse. She laughed fit to burst her wrapper.
1914		Bulletin (Sydney) 13 Aug. 10/2: Ginger: ‘’Ere! Wot d’yer mean be knockin’ me tart in the jaw?’ / Micko: ‘So ’elp me, Ginger, it was a haccident. I’ll let yer give my tart a woodner if yer like.’.
1937		Sun. Times (Perth) 21 Feb. 3/7: A big muscular man of 6 ft. 2 in. and a mighty stousher landed a woodener on the aide’s jaw.

2. in fig. use, something, e.g. an excess of drink, that ‘knocks one out’.

1906

Gadfly (Adelaide) 28 Mar. 9/1: Anyhow, me an’ ’im goes on a bit of a bender up in Wirapilla, where we’re workin’ on a sawmill. Things is dead slow, an’ we can’t even raise a dawg fight, so when Mick gets a woodener an’ goes to lay down behind the pub, I goes up the street lookin’ fer amusement like.