Why were dancers called B-boys and B-girls at early hip-hop parties?

At early hip-hop parties, dancers were called B-boys and B-girls because they performed during the "break"—the percussive instrumental section of a song that DJ Kool Herc isolated and extended using two turntables to create a continuous flow of music.123

Recognizing that these rhythmic breaks encouraged guests to dance more energetically, Herc would "call out" individual dancers to perform their moves during these specific segments, referring to them as "break-boys and break-girls," which was eventually shortened to "B-boys and B-girls". The term "break" itself refers to these isolated drum patterns, also known as breakbeats, which provided the foundation for the improvisational, acrobatic style of break dancing.1243