Nobody knows. I remember there was a similar thread on old forums, but I can't find it. If I remember correctly, even said it had no meaning. Multi-player might be a good answer if you need one.
MP means MP PocketMine. Recursive acronym, that's all. Not true. Why would the personl who made up the name of PocketMine-MP call it PocketMine-MultiPlayer? I think PocketMine-MP is the best answer for Levi's question right now.
PHP: Hypertext Preprocessor PHP in itself is also one recursive acronym too what make PMMP different is is the acronym is in the end, unlike most they always have it in the end
Seriously I don't see how that's rude. I'm not a human, so I might have missed it. Mind explaining? <Insert the same image with joke changed to rude>