Mine came from the grand old days of computing, when we still used mainframes.
I was working for a government contractor, and the go-to guys that really knew the mainframes best (DEC VAX 11/780's, 11/750's, and the newest 8974's) were unofficially nicknamed the "Beastmasters".
I was added to their unofficial ranks when I was optimizing the distributed cluster to finish a project in time and I ended up eating 90% of the cluster's cycles - just for me. Messed up all the other engineers and programmers, but I got my research stuff done in time!
I've had the nickname online in some way, shape, or form since the mid 80's. And I still have all of my VAX manuals on my bookshelf. I still can't bear to toss them.