Question: why aye instead of yes?
Answer: The word aye (/aɪ/), as a synonym for yes in response to a question, dates to the 1570s and, according to the Online Etymology Dictionary, is of unknown origin; it may derive as a variation of the word I (in the context of "I assent"); as an alteration of the Middle English yai ("yes"), or from the adverb aye (meaning ...