Etymology
Uncertain; perhaps:
* related to Old French fornoiier, fornier (“to deny”), from for- (prefix expressing error, exclusion, or inadequacy) + noiier, nier (“to deny”) (compare Late Latin forīsnegāre (“to renege, repudiate”), where the Frankish for- is rendered into Latin as forīs), from Latin negāre (“to deny; to refuse, say no; to reject, turn down (something)”), from nē (“no; not”) + aiō (“to affirm, say ‘yes’”)) (for the word ending, compare reneague (“to refuse to follow suit in a card game, renege; to deny, refuse; act of refusing to follow suit in a card game”) (Britain, dialectal)); or
* from feign (“to pretend”) + ague (“intermittent fever; (obsolete) acute fever”), or French aigüe (“(medicine) acute”) (as in maladie aiguë (“acute illness”)), literally “to act sick”.