aye (adv.)
"always, ever," c. 1200, from Old Norse ei "ever" (cognate with Old English a "always, ever"), from PIE *aiw- "vital force, life, long life, eternity" (source also of Greek aion "age, eternity," Latin aevum "space of time;" see eon).
aye (interj.)
word of assent to a question, 1570s, of unknown origin; perhaps a variant of I, meaning "I assent;" or an alteration of Middle English yai "yes" (see yea); or from aye (adv.) "always, ever."