A 'Baenot' is a person who you previously referred to as 'bae'. So, if something happened to damage that relationship, you would from then on resort to referring to them as the 'baenot'.
This could also be a word used instead of sarcastically saying 'oh look, here comes the bae' ... 'not'. However, it is most commonly used to refer to an 'ex-bae'

n. The birth name of somebody who has changed their name. Most commonly attributed to trans people, but can be attributed to any person who has changed their name. (sometimes written as two words: dead name)

v. 1. To call somebody by their deadname.
v. 2. To out somebody's deadname to the public.

When you and another person flirt, act cute, may have hooked up once or twice but both know it will never be more than that. Yet you enjoy the attention and flirtatious behavior.