The original name for bboy.They call it beat boy because of the people dancing to the beat.
Back in the day bboys don't have a type of gymnastic dance, so bboy stands for beat boy because of the people that started breaking were just people that were hyper and energetic and moving around hitting beats and listening to music created break dancing.

Beat Boy means Break Boy, B-Boy, or Bronx Boy.
Back in the days of original Hip Hop the original Beat Boys would dress as fly as possible, and part of the flava of a Beat Boy would be how he could do all of his moves and never get dirty.
Beat Boys would go to a jam, dance with some females, socialize, and when the right break beats came on, they'd get down, and after gettin down, they would get back to partying.