Green’s Dictionary of Slang

1. (Aus.) a peasant, an unsophisticated person.

[1945		Baker Aus. Lang. 200: Dad and Dave. Two notable figures in the hierarchy of Australian popular literature and humour. They appeared first in A. H. Davis’s ‘On Our Selection’ (1899) and have been used for many years in a radio serial entitled ‘Dad and Dave.’].
1974		G. Blainey Australian 4 Oct. 8: On the farmlands the trees were ring barked in their hundreds of thousands, and behind post-and-rail fences they often stood in their pale cemeteries for five or fifteen years before Dad and Dave burned them down [GAW4].
1984		Australian 23 Feb. 11: If Dad and Dave and Mabel were still battling it out on their selection today the chances are the Australian taxpayer would be footing the bill [GAW4].

2. (N.Z. prison, also Dad and son) two very close inmate friends.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 52/1: Dad and Dave n. 1 two inmates who are very good friends and spend much of their time together [...] dad and son n. = Dad and Dave sense 1.

3. (N.Z. prison) .

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 52/1: Dad and Dave n. 2 a shave.