"action of perceiving," late 14c., verbal noun from discern. As a present participle adjective, attested from c.1600.
late 14c., from Old French discerner (13c.) "distinguish (between), separate" (by sifting), and directly from Latin discernere "to separate, set apart, divide, distribute; distinguish, perceive," from dis- "off, away" (see dis-) + cernere "distinguish, separate, sift" (see crisis). Related: Discerned; discerning.