Green’s Dictionary of Slang

1. money, esp. as gambling winnings or losses or as a large sum.

1934		C. Drew ‘Shakespeare Harry’s Runner’ in Bulletin 27 June 50/3: ‘[I]f you take my tip you’ll back him for a motzer yourself’.
1955		N. Pulliam I Travelled a Lonely Land (1957) 236/1: motser (motza, motzer) – quite a big chunk of money.
1967		‘Whisper All Aussie Dict.’ in Kings Cross Whisper (Sydney) xxxvi 4/2: motzer: A lot, a great amount of anything.
1983		J. Byrell (con. 1959) Up the Cross 8: ‘I fair dinkum dropped a motzah’.
1986		R.G. Barrett Real Thing 24: Her first husband [...] was accidentally killed at workleaving Parrie a motza.
1996		J. Byrell Lairs, Urgers & Coat-Tuggers 164: Yair - and several rails books, including one of the Waterhouses, I think, were plucked for a motza.
2001		(con. 1945–6) P. Doyle Devil’s Jump (2008) 98: We can sell these coupons ourselves [...] we’ll make a motza on them.
2002		R.G. Barrett Mystery Bay Blues 265: An antique like this, he mused —solid gold and inlaid with black opal — it’d be worth a motza.
2007		L. Redhead Cherry Pie [ebook] Gonna need a motza if he wants to try his luck in the States.
2017		T. Spicer Good Girl Stripped Bare 297: Cosmetics companies have made a motza out of masking women.
2021		C. Hammer Opal Country 395: ‘Told me it was a goldmine, said he was making a motza’.

2. a ‘certainty’, which will guarantee such a win.

1936		‘Banjo’ Paterson Shearer’s Colt 180: I got it. It’s a motzer. It’s a schnitzler.
1996		J. Byrell Lairs, Urgers & Coat-Tuggers 48: [A] great idea for making a professional motza of a killing at that year’s Melbourne Cup meeting.