insipient

“foolish,” mid-15c., from Latin insipientem (nominative insipiens) “unwise, foolish,” from in- “not” (see in- (1)) + sapientem (see sapient). “Now mostly, or wholly, disused to avoid confusion with incipient” [OED].

early 15c., “lack of wisdom, foolishness,” from Old French insipience, from Latin insipientia “folly,” from insipientem (see insipient).