mid-14c., gestour, jestour "a minstrel, professional reciter of romances," agent noun from gesten "recite a tale" (a jester's original function), from geste "action, exploit" (see jest (n.)). Sense of "buffoon in a prince's court" is from c. 1500. Sterne (1759) uses jestee, but it is rare.

"professional jester; a minstrel," c. 1500, from Latin ioculator "a joker, jester," from iocus "pastime; a joke" (see joke (n.)).

1580s, "function or manners of a stage clown or jester," from clown (n.) + -age. From 1630s as "actions or behavior of a rustic."

also crosspatch, "peevish person," usually female, c. 1700, from cross (adj.) "ill-tempered" + patch (n.2) "professional jester," or possibly from or reinforced by patch (n.1) "piece."

"trifling, of no value; invalid, futile," c. 1600, from Latin nugatorius "worthless, trifling, futile," from nugator "jester, trifler, braggart," from nugatus, past participle of nugari "to trifle, jest, play the fool," from nugæ "jokes, jests, trifles," a word of unknown origin.

also fool's-cap, 1630s, "type of cap worn by a jester;" see fool (n.1) + cap (n.). From c. 1700 as a type of writing paper, so called because it originally was watermarked with a jester's cap.

"wandering minstrel of medieval times," 1779, a revival in a technical sense (by modern historians and novelists) of Norman-French jongleur, a variant of Old French jogleor "minstrel, itinerant player; joker, juggler, clown" (12c.), from Latin ioculator "jester, joker" (see juggler).

1540s, "type of pantomime dance;" 1580s, "professional comic fool;" 1590s in the general sense "a clown, a joker;" from French bouffon (16c.), from Italian buffone "jester," from buffa "joke, jest, pleasantry," from buffare "to puff out the cheeks," a comic gesture, of echoic origin. Also see -oon.

c. 1100, iugulere "jester, buffoon," also "wizard, sorcerer," from Old English geogelere "magician, conjurer," also from Anglo-French jogelour, Old French jogleor (accusative), from Latin ioculatorem (nominative ioculator) "joker," from ioculari "to joke, to jest" (see jocular). The connecting notion between "magician" and "juggler" is dexterity. Especial sense "one who practices sleight of hand, one who performs tricks of dexterity" is from c. 1600.

"morbid fear of clowns," by 2001 (said in Web sites to date from 1990s or even 1980s), a popular term, not from psychology, possibly facetious, though the phenomenon is real enough; said to be built from Greek kolon "limb," with some supposed sense of "stilt-walker," hence "clown" + -phobia.

Ancient Greek words for "clown" were sklêro-paiktês, from paizein "to play (like a child);" or deikeliktas. Greek also had geloiastes "a jester, buffoon" (from gelao "to laugh, be merry"); there was a khleuastes "jester," but it had more of a sense of "scoffer, mocker," from khleuazo "treat with insolence." Other classical words used for theatrical clowns were related to "rustic," "peasant" (compare Latin fossor "clown," literally "laborer, digger," related to fossil).

Coulrophobia looks suspiciously like the sort of thing idle pseudo-intellectuals invent on the internet and which every smarty-pants takes up thereafter; perhaps it is a mangling of Modern Greek klooun "clown," which is the English word borrowed into Greek.