The country didn't have a unified system of liquid measurement in the 19th century because the Afrikaners used the Dutch gallon [3.3947 (≈3.4)?
The firkin, kilderkin, barrel, hogshead, and butt were traditional British measurements of capacity for standard ale and beer containers.
Dutch sailors drank the local wine to combat scurvy and exported barrels of it back to Europe.
This was followed by the British government's policy of encouraging the wine and brandy industry in South Africa in the early- to mid-19th century through subsidies and low tariffs.
(Their recent isolation during Napoleon's Continental System impressed upon them that they would potentially need alternative sources of European commodities in the future.)
The kanne, anker, ahm, and legger are obsolete 17th century Dutch measurements of capacity that were used for standard containers of wine and spirits.