My theory NOW!!: Mickey and Minnie start with “m” Donald and Daisy start with “d” Bendy and Boris start with “b”
Here’s a screenshot that I took from being random searching things up. I don’t mind if this is true but ThE (game) cReAtOrS hAd LiEd To Us!! Plus Bendy does wear a skirt so we might’ve assume he’s a boy or just loves to screw gender stereotypes