The name is either a combination of three Nama words: 'tconsiep' (an elbow projecting into the river), 'nias' (a rocky surface), and 'tcaans' (thorntrees), or it is a derivative of the Nama word meaning 'watering place for cattle'. Whatever its origin, the name did not deter a white prospector, Edwells, settling on the Orange River in 1909.
Farmers, realising the value of irrigating the area, bought 12 000ha of land from Edwells in 1916. In the same year, 63 plots were surveyed and taken up. A 10km canal serving 70 families was built by Japie Lutz and, today, citrus, lucerne, beans and other crops are grown at Onseepkans. The village itself is a mission station run by the Roman Catholic Father of Pofadder.