mid-14c., "to form a mental image of," from Old French imaginer "sculpt, carve, paint; decorate, embellish" (13c.), from Latin imaginari "to form a mental picture, picture to oneself, imagine" (also, in Late Latin imaginare "to form an image of, represent"), from imago "an image, a likeness," from stem of imitari "to copy, imitate" (from PIE root *aim- "to copy"). Sense of "suppose, assume" is first recorded late 14c. Related: Imagined; imagining.
"intellect, intelligence," 1820, from Greek noēsis "intelligence, thought," from noein "to see, perceive, have mental perception," from noos "mind, thought" which is of uncertain origin.
"tending or serving to refresh, invigorating," 1570s, present-participle adjective from refresh (v.). Mental or spiritual sense is attested from 1690s. Related: Refreshingly.
"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.