late Old English gewær "watchful, vigilant," from Proto-Germanic *ga-waraz (source also of Old Saxon giwar, Middle Dutch gheware, Old High German giwar, German gewahr), from *ga-, intensive prefix, + *waraz "wary, cautious," from PIE root *wer- (3) "perceive, watch out for."
Among hundreds of Middle English words it formed are yfallen, yhacked ("completely hacked," probably now again useful), yknow, ymarried, ywrought.
Proto-Indo-European root meaning "perceive, watch out for."
It forms all or part of: Arcturus; avant-garde; award; aware; beware; Edward; ephor; garderobe; guard; hardware; irreverence; lord; panorama; pylorus; rearward; regard; revere; reverence; reverend; reward; software; steward; vanguard; ward; warden; warder; wardrobe; ware (n.) "manufactured goods, goods for sale;" ware (v.) "to take heed of, beware;" warehouse; wary.
It is the hypothetical source of/evidence for its existence is provided by: Latin vereri "to observe with awe, revere, respect, fear;" Greek ouros "a guard, watchman," horan "to see;" Hittite werite- "to see;" Old English weard "a guarding, protection; watchman, sentry, keeper."
c. 1600, "knowing, privy to" (poetic), from Latin conscius "knowing, aware," from conscire "be (mutually) aware," from assimilated form of com "with," or "thoroughly" (see con-) + scire "to know" (see science). The Latin word probably is a loan-translation of Greek syneidos.
The sense of "knowing or perceiving within oneself, sensible inwardly, aware" is from 1630s, perhaps a shortening of conscious to oneself (1620s). Also compare the Latin sense evolution in conscience. From 1650s as "aware (of a fact)." Sense of "active and awake, endowed with active mental faculties" is from 1837. Related: Consciously.