From Old French 'waitier' (to watch), from Frankish *wahton — shifted from alert vigilance to passive expecting.
To remain in a place or stay in a state of inaction until an expected event happens or someone arrives.
From Old Northern French 'waitier' (to watch, guard, lie in wait), from Frankish *wahtōn (to watch, guard), from Proto-Germanic *wahtāną (to watch, be awake), from PIE root *weǵ- (to be strong, lively, awake). The original meaning was not passive inaction but active vigilance — to lie in wait was to keep watch, as a sentinel or an ambusher. The shift from 'watch alertly' to 'remain passively until something happens' occurred during the Middle English period. Key
English 'wait' and 'watch' are etymological doublets — both descend from the same Proto-Germanic root *wahtāną (to watch, be awake), but 'watch' came directly through Old English while 'wait' took a roundabout journey through Frankish into Old French and back into English after the Norman Conquest. A word of Germanic origin returned to a Germanic language disguised as a French borrowing.