Lewis Short
effĭcĭentĭa (noun F) : efficio
* Efficient power, efficiency, influence (rare; mostly in philos. lang.),Cic. N. D. 2, 37, 95; id. Fat. 9, 19: spiritalis, Hil. in Psa. 131, 24: inenarrabilis,id. Trin. 3, 18; Lact. Opif. D. 19, 7.
Charlton T. Lewis, Charles Short, A Latin Dictionary