Green’s Dictionary of Slang

1. (Aus.) to pretend.

1905		Bulletin (Sydney) 14 Dec. 27/1: Up on the Towers in ’94 I knowed a funny hair-shifter that fell in bad. He had as many tricks as a monkey, an’ on Sat’day, when he’d have one or two in and some blokes waitin’ a turn, he was sure to pull somebody’s leg, and, as he wuz credited with a dirty left, the bloke what was ’ad useter dicken he liked it.
1916		C.J. Dennis ‘To the Boys Who Took the Count’ in Moods of Ginger Mick 101: Now it’s dickin to style if yer playin’ the game / If it’s marbles, or shinty, or war.

2. (Aus.) to express doubt.

1924

G.H. Lawson Dict. of Aus. Words And Terms 🌐 DICKEN—To express doubt.