mid-15c., cognicioun, "ability to comprehend, mental act or process of knowing," from Latin cognitionem(nominative cognitio) "a getting to know, acquaintance, knowledge," noun of action from past participle stem of cognoscere "to get to know, recognize," from assimilated form of com"together" (see co-) + gnoscere "to know," from PIE root *gno- "to know." In 17c. the meaning was extended to include perception and sensation.