Green’s Dictionary of Slang

excellent, outstanding.

1907		Sun (Kalgoorlie) 31 Mar. 7/2: The latest abbreviation of a new slang word ‘bonz’ was applied to the splendid supper provided by the ladies.
1913		Dly Teleg. (Sydney) 23 Apr. 15/6: ‘Mother, we marched with a band to-day. Through the street. Oh, It was bonz – I mean splendid’.
1914		Williamstown Advertiser (Vic.) 10 Oct. 4/2: [advert] ‘The Princess Shoe.’ A dainty Glace Kid shoe in anklette or Court. A bonze little line for ladies, 11/0.
1921		Sydney Stock & Station Jrnl 22 Mar. 4/1: The Band was bonze; you could easily tell that the Big Drummer was a splendid player.
1936		Uralla Times (NSW) 8 June 2/6: They say [...] That the children reckon it was ‘bonz’.
1933		Western Mail (Perth) 24 Aug. 2/5: As the nurse tiptoed to the balcony and threw the empty bottle over, my neighbour turned towards me and whispered, ‘That was bonze, Dig!’.
1947		Truth (Brisbane) 12 Oct. 22/2: Now boys at St. John’s, / Saying Hardie is ‘bonze,’ / Are all for rewardin’ the Warden.