The name De Aar refers to the underground water supply occurring in arteries. The name De Aar was given to a property first surveyed in September 1837, and subdivided in 1839. The subdivision, purchased by Jan Gabriel Vermeulen, was named De Aar for a strong perennial spring there. Surveys carried out in 1881 identified this piece of land as suitable for the primary junction for interior railways on the Cape Government Railways system.
All the water used in De Aar comes from bore holes of which a major part comes from Burgerville. Burgerville was a flourishing town in the early 1930’s, but the town council of De Aar wanted the water from the area on which Burgerville sited. The whole town was thus bought out. 54 Bore holes in areas surrounding the town, ensures the water supply.