Green’s Dictionary of Slang

1. (Aus.) fast, efficient, keen.

1901		Bulletin (Sydney) 13 Jul. 23/1: Most of the comps. were taking holidays, biz. being down below zero. One of them, however, with a pertinacity that becomes monotonous, called three and four times a day on the chance of work. ‘Look here, Jimmy,’ said the boss at last, ‘don’t be so very sudden. When I get any work in I’ll send for you.’.
1919		W.H. Downing Digger Dialects 48: sudden — Quick; thick and heavy. ‘You’re sudden, aren’t you?’ A protesting question applied to a man who walks away with something belonging to someone else.

2. (orig. Aus.) brutal, ruthless, drastic; of clothes, garish; also adv.

1901		H. Lawson ‘That Pretty Girl on the Army’ in Roderick (1972) 483: The Bogan’s face, as representing free thought, was a bit sudden for them.
1914		E. Dyson Spats’ Fact’ry (1922) 59: Don’t be sudden, blokie.
1919		D. Runyon ‘A Tale of two Fists’ XIX in Pittsburgh Press (PA) 25 May 25/1: ‘We both had on coats that fit us rather sudden’.
1925		Wodehouse Carry on, Jeeves 5: [The suit] was perhaps rather sudden till you got used to it.