Some clapping fun facts from The Encyclopedia of Trivia
Ancient Greek audiences stamped their feet rather than clapping their hands to applaud.
One theory is that the tradition of clapping dates back to 1473 and an outbreak of cholera. Slapping your hands together was a signal to those around that you were infected. Eventually it became a token of applause, a way of keeping time, and then, by the 1800s, a musical device in its own right.
In Japan, rhythmic handclapping, or tejime, is used ceremonially to celebrate the end of a special event.
A group of people that are hired to clap at a performance are called a claque.