Origin: 1325–75; Middle English simplicite (< Old French simplicité) < Latin simplicitās simpleness, equivalent to simplici- (stem of simplex) simplex + -tās-ty2
late 14c., from O.Fr. simplicite (Fr. simplicité), from L. simplicitatem (nom. simplicitas) "state of being simple," from simplex (gen. simplicis) "simple" (see simplex). Sense of "ignorance" is from 1510s, that of "plainness" is from 1520s.