mid-15c., "act or fact of understanding," from Old French comprehénsion (15c.), and directly from Latin comprehensionem (nominative comprehensio) "a seizing, laying hold of, arrest," figuratively "perception, comprehension," noun of action from past participle stem of comprehendere "to take together, to unite; include; to comprehend, perceive" (to seize or take in the mind), from com "with, together," here probably "completely" (see com-) + prehendere "to catch hold of, seize," from prae- "before" (see pre-) + -hendere, from PIE root *ghend- "to seize, take." From 1540s as "the act of including;" from 1590s as "capacity of the mind to understand." In reading education, from 1921.