early 13c., "an emotion of the mind, passion, lust as opposed to reason," from O.Fr. affection, from L. affectionem (nom. affectio) "inclination, influence, permanent state of feeling," from affec-, pp. stem of afficere "to do something to, act on" (see affect (n.)). Sense developed from "disposition" to "good disposition toward" (late 14c.).