I am a bass guitarist. This used to be my profession; now it's a paying hobby. You gotta love hobbies that pay for themselves.
Anyway, often groups will introduce the band members during the performance. One night, the singer was introducing the band, and when he got to me, he said, "...and on the bottom, we got 'em. Bass in your face." For the non-musical, being on the bottom refers to the bassist's function of providing the low frequency tones that make guitarists and singers more tolerable. ;>)
So, for some reason, from that night on, musicians in the area have called me Bottomgottem.
That's the story.