1590s, from ill (adv.) + advised, past-participle adjective from advise (v.) in its original (but now obsolete) reflexive sense "take thought, consider." Related: Ill-advisedly.
Entries linking to ill-advised
ill adv.
c. 1200, "wickedly; with hostility," from ill (adj.). Meaning "not well, poorly" also is from c. 1200. It generally has not shifted to the realm of physical sickness, as the adjective has done. Ill-fated recorded from 1710; ill-informed from 1824; ill-tempered from c. 1600; ill-starred from c. 1600. Generally contrasted with well, hence the useful, but now obsolete or obscure illcome (1570s), illfare (c. 1300), and illth.
advise v.
late 13c., avisen "to view, consider" (a sense now obsolete); late 14c., "to give counsel to," from Old French aviser "deliberate, reflect, consider" (13c.), from avis "opinion," from phrase ço m'est à vis "it seems to me," or from Vulgar Latin *mi est visum "in my view," ultimately from Latin visum, neuter past participle of videre "to see" (from PIE root *weid- "to see"). The unetymological -d- is from 16c. Related: Advised; advising.