Green’s Dictionary of Slang

dacca n.

(Aus.) marijuana.

1977		Sun-Herald (Sydney) 16 Oct. 63: Some new words emerge [among the unemployed youth of the western suburbs] like ‘dakker’ for drugs [GAW4].
1982		Sydney Morning Herald 18 Sept. 1: At a teenage party you may be offered dacca or spot. Called marihuana by some, it’s likely to send you off your face [GAW4].
2002		R.G. Barrett Mystery Bay Blues 155: Grace looked at the two joints [...] and the bag of dacca.
2012		L. Redhead ‘Grassed’ in Crime Factory: Hard Labour [ebook] The Sydney punters couldn’t get enough of [...] the dakka.

In phrases

dack up (v.)

(N.Z.) to smoke marijuana.

1992

A. Duff One Night Out Stealing 102: You all [...] drank more piss, went outside to dack up with a few of the boys.