Green’s Dictionary of Slang

(S.Afr.) a drink composed of whisky or rough brandy, Pontac (a sweet red dessert wine) and ginger-beer.

1873		F. Boyle To Cape for Diamonds 28: Home-made ginger-beer, called in our camp parlance a ‘pickaxe’. [Ibid.] 125: [He] cools his brow and whets his hopes in pontac and gingerbeer, ‘pickaxe,’ or some such compound.
1876		F. Boyle Savage Life 28: Before him, on a board smoothed with dirt, stood the filthiest of all glasses, containing a turgid compound of pontak wine, ‘cape smoke’, and home-made ginger-beer, called in our camp parlance a ‘pickaxe.’ [DSAE].
1887		A.B. Ellis S. Afr. Sketches 81: He was forced to take shelter behind the bowl of his pipe, and to reinvigorate himself with a ‘pick-axe’, by which designation a fiery mixture of Cape Smoke, Pontac, and ginger-beer, was known at the Fields .
1913		C. Pettman Africanderisms 370: Pick-axe, The slang name of a fiery mixture of Cape smoke, pontac, and ginger-beer, in much request in the Diamond Fields in the early days.