"pertaining to, performed by, or originating in the intellect," 1650s, from Greek noētikos "intelligent," from noēsis "a perception, intelligence, thought" (see noesis). Related: Noetical (1640s).
c. 1600, "having an overweening opinion of oneself" (short for self-conceited, 1590s), past-participle adjective from conceit (v.) "conceive, imagine, think" (1550s), a now-obsolete verb from conceit (n.). Earlier it meant "having intelligence, ingenious, witty" (1540s). Related: Conceitedly; conceitedness.
"to explain, as a man to a woman, in a way that she feels insults or ignores her intelligence and experience in the matter," by 2008, from man (n.) + second element from explain (v.). The form 'splain, as a clip of explain, had been used at least since the 1960s as a colloquialism. Related: Mansplained; mansplaining.
In reference to devices, the sense of "behaving as though guided by intelligence" (as in smart bomb) first attested 1972. Smarts "good sense, intelligence," is first recorded 1968 (Middle English had ingeny "intellectual capacity, cleverness" (early 15c.)). Smart cookie is from 1948.