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."

"always, ever," c. 1200, from Old Norse ei "ever" (cognate with Old English a "always, ever"), from Proto-Germanic *aiwi-, extended form of PIE root *aiw- "vital force, life; long life, eternity" (source also of Greek aiōn "age, eternity," Latin aevum "space of time").