prime [LME] At the start of the 16th century to prime was ‘to fill or load’, especially a gun for firing. It was probably based on Latin primus ‘first’, also the source of the adjective prime [LME], since priming something is the first operation you perform before using it. Priming the pump [E19th] refers to pouring a small amount of water into a mechanical pump to establish suction so that it can begin to work properly. Primus is also the source of primary [LME]; primeval (M17th from primus and aevum ‘age’); and primitive [LME]. It is probably also the source ofprim [L17th], via a Provençal variant prin meaning ‘excellent, delicate’. Prim blended with sissy givesprissy [L19th].