NieR Automata: Dark Apocalypse - Hints and Predictions

[Daralii]

My understanding is that it's a pun, in that 2B rhymes with 2P, and 2P is an abbreviation often used for Second Player - and it's usually the second player that gets the variant skin.

If there's more to it then that, I'm unaware. 2P is a fan nickname for 2B when she's wearing the second-player alternate skin.

Yoko Taro took a liking to it and now 2P is canon.