The word clap comes from Old English claeppan, which meant "to beat" or "throb", has some Germanic relatives, and is probably onomatopoeic in nature. That's simple and relatively uninteresting, but some fascinating slang words have derived from the word. Starting all the way back in the 1580s, gonorrhea began to be referred to as the clap, which was probably partially influenced by the "throb" meaning (due to the painful feelings associated with the STD) and the Old French word clapoire, meaning "brothel". In recent years, getting clapped has also started to emerge in teenage argot as meaning "to be defeated" in both a literal and metaphorical sense, which is probably influenced by the more physical connotations of the word, and clapping can have a definition of "having sex", for similar reasons.
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd