Aye is the spelling used by Parliament, but the antipodean, squirrel-like animal the aye-aye was not named after that baying crowd but the sound it makes. The New Yorker once reviewed a Barry Manilow show: "The noes have it."
CHAIN OF association from yesterday's "awe" makes one wonder about aye aye, whose origins prove obscure. It first appeared at the end of the 16th century, when it was spelt I and defined in an early grammar as "I for Yes, is used in a hasty or merry Way, as I Sir, I Sir." Johnson's supposition that it comes from the Latin aio is fanciful but his definition is neat: "it is a word by which the sense is enforced". It is possible that, through a path of dialects, it derives from ay, whose meaning slid from always to a mere certainly or yes.