Board Thread:Questions and Answers/@comment-93.36.207.144-20130923115606/@comment-29164710-20161006122702

Ryan said himself in a post on the Subreddit

The BM stands for "Been Mawed" referring to the Halo level "The Maw" which is a level him and his friends liked and would play on a lot for tournaments

And the Vagabond is from what I remember like a call or something from a character from Wing Commander III