"pertaining to mental conception," 1820 (there is an isolated use from 1662), from Medieval Latin conceptualis, from Latin conceptus "a collecting, gathering, conceiving," past participle of concipere "to take in" (see conceive). Perhaps it emerged to go with the distinctly mental sense of conception, as it seems rarely, if ever, to have been used in the physical sense. Conceptional "pertaining to or having the nature of (physical) conception" is from 1832.
