A court buffoon or court jester was an individual who was employed as a fool for entertainment.
In the Earth movie The Court Jester, Danny Kaye played the titular fool. (ENT: "Doctor's Orders")
Alexander was brought to the planet Platonius as a court buffoon for the Platonians, a fact he related to the USS Enterprise landing party in 2268. (TOS: "Plato's Stepchildren")