1510s, from Late Latin insensatus "irrational, foolish," from Latin in- "not" (see in-(1)) + sensatus "gifted with sense" (see sensate). Insensate means "not capable of feeling sensation," often "inanimate;" insensible means "lacking the power to feel with the senses," hence, often, "unconscious;" insensitive means "having little or no reaction to what is perceived by one's senses," often "tactless."