Green’s Dictionary of Slang

1. criminally obtained.

1846		Swell’s Night Guide 58: Half-a-bull is half-a-bull; it’s multa denarly if you cops a multa swag.
1850		[as 1846].
1887		W.E. Henley ‘Villon’s Straight Tip’ in Farmer Musa Pedestris (1896) 176: Suppose you screeve, or go cheap-jack? / [...] / How do you melt the multy swag? / Booze and the blowens cop the lot.

2. of people and things, bad, unpleasant.

1880		Bulletin (Sydney) 28 Sept. 8/1: The Franzini Variety Company [...] did not fizzle; the houses were ‘multy’ and the shutters were up.
1895		Truth (Sydney) 14 Apr. 3/6: He was a travelling Union delegate [...] then, when that grew a bit ‘multy’ he turned his talents to engineering.
1904		Sun. Times (Perth) 27 Mar. 8/3: Working in an ice factory oughtn’t to be too multy a job this weather.
1908		Truth (Brisbane) 19 Apr. 9/3: I do know this are a subject / Which are multy like & stale.
1913		Truth (Sydney) 12 Jan. 11/4: Round in Lundon, day or nite, / Are some most pecooliar doin’s— / Fairly multy, and no skite.