Initially, the term was used for a civilian official in a local government district (Drostdy) of the Cape Colony, acting as and invested with the authority of a military officer and empowered to act as a magistrate. The Field Cornet was subject to the Landdrost of such a district and acted as his representative. As such, the Field Cornet performed important functions in administrative, judicial and police matters. In addition, in peacetime the Field Cornet was the head of the militia and was responsible for maintaining law and order in his area.
However, the term later came to denote a military rank equivalent to that of a lieutenant in the Boer armies as well as in the South African Army between 1960 and 1968. A Second Lieutenant was referred to as an assistant field cornet.