1650s, "sense of touch or feeling" (with an isolated instance, tacþe from c.1200), from Latin tactus "a touch, handling, sense of touch," from root of tangere "to touch" (see tangent, adj.). Meaning "sense of discernment in action or conduct, diplomacy, fine intuitive mental perception" first recorded 1804, from development in French cognate tact. The Latin figurative sense was "influence, effect."