Originally the term clown meant a vulgar or boorish person, a peasant. It now means a comic entertainer.
In Elizabethan theatre the clown was a specialised actor who played comic parts, probably accompanied by physical activities, such as dancing, specific to the actor. The type was later developed in the harlequinade and pantomime, and acquired specialised make-up and costume. The most famous clown, Grimaldi, was renowned for his acrobatic abilities.
Clowns are a traditional part of circuses, having costumes and make-up personalised and trademarked to each performer.
There is a longstanding view of clowns (and harlequins) as melancholy behind their comic personas, illustrated in both art and literature.