Facepunch, looking to move up in the world, arrived on /co/ve and, seeing that there was opportunity to be found, quickly invited his associate Crotch Rocket to come join him. Together they formed a mercenary group, working for whoever paid them.
The group didn't actually have a name until after Arms guy joined and Facepunch discovered they could "combine" to form a "giant robot".
Face Punch is laying on the ground, beaten, Crotch Rock-it equally beaten, Arms guy is still standing, not that beaten.And so the name Full Body Beat Down came to be.
Face Punch: "Damn, these heroes are tough, we'll have to use... *that*!"
Crotch Rock-it: "What? Since when have you been hot blooded?"
Arms guy: [Floating question mark above his head]
Face Punch: "Just be ready to get on Rock's shoulders, Arms."
Running and positioning
Face Punch: "NOW! UNION!"
Somehow the "transformation" sequence was so stupid and silly that it caused everyone else to pause, given them a chance to get some hits in before blasting off.
Somehow they actually are stronger like this.
Their body part theme was coincidental.