Meaning

noun a sudden very loud noise

noun a common venereal disease caused by the bacterium Neisseria gonorrhoeae; symptoms are painful urination and pain around the urethra

noun a sharp abrupt noise as if two objects hit together; may be repeated

originUncertain. Probably from Old French clapoir (“bubo, inflammation from infection”), from clapier (“brothel”). May also be from old, unsafe treatments for gonorrhea, such as clapping the penis between a book and a hard surface to break up obstructions in the urethra and permit urination. Attested from the 16th century.

Etymology from Wiktionary, CC BY-SA 3.0