Coulrophobia is a fear of clowns.
The term is of recent origin, probably dating from the 1980s, and according to one analyst, "has been coined more on the Internet than in printed form because it does not appear in any previously published, psychiatric, unabridged, or abridged dictionary." However, the author later notes, "regardless of its less-than-verifiable etymology, coulrophobia exists in several lists."
The prefix coulro- may be a neologism derived from the Ancient Greek word κωλοβαθριστής (kōlobathristēs) meaning "stilt-walker."[nb 1] Although the concept of a clown as a figure of fun was unknown in classical Greek culture, stiltwalking was practiced. The Online Etymology Dictionary states that the term "looks suspiciously like the sort of thing idle pseudo-intellectuals invent on the Internet and which every smarty-pants takes up thereafter".
According to a psychology professor at California State University, Northridge, young children are "very reactive to a familiar body type with an unfamiliar face". Researchers who have studied the phobia believe there is some correlation to the uncanny valley effect.
A study conducted by the University of Sheffield found that the children did not like clown décor in the hospital or physicians' office settings. The survey was about children’s opinions on décor for an upcoming hospital redesign. Dr Penny Curtis, a researcher, stated "We found that clowns are universally disliked by children. Some found the clown images to be quite frightening and unknowable."
In popular culture
In July 2006, the Bestival, a three-day music festival held in England, had to withdraw a request to festival goers to come dressed as clowns due to the unexpectedly high prevalence of claimed coulrophobia among the potential audience.
In a 1992 episode of Seinfeld ("The Opera" S4, E9) recurring character "Crazy" Joe Davola plays a clown dressed as the character Pagliaccio from the opera Pagliacci. Davola approaches Kramer, who thinks the clown looks familiar. Kramer mentions that he was scared of clowns. The clown then asks Kramer if he is still scared of clowns, to which Kramer uneasily answers, "Yeah."
Coulrophobia can be a plot device used to show how the protagonist must overcome his fears in order to vanquish the enemy. Examples include the 2009 film Zombieland, in which a character must overcome his fear in order to kill a zombie clown.
Coulrophobia can also be used for humor, such as in an episode of Frasier ("Boo!" S11,E16), in which Frasier has a patient a children's nurse who is afraid of clowns. One day, Frasier gets a clown costume to transform himself in to a clown in front of the scared patient in an attempt to cure her. Martin, Frasier's Father has been sneaking up on him and scaring him throughout the episode so Frasier decides to dress up as a clown to scare his father. Martin has a heart attack and is taken to the hospital. Frasier follows, dressed in his clown costume where he bumps in to his patient who screams hysterically upon laying eyes on him.
In The Simpsons episode "Lisa's First Word", Homer tries to build a bed for Bart after he outgrows his crib, and fashions the headboard into a clown. However, instead of being the "fun friend" Homer intends it to be, it triggers insomnia in Bart, who keeps repeating "can't sleep, clown will eat me." The phrase became an Internet meme and inspired the Alice Cooper song "Can't Sleep, Clowns Will Eat Me".
In Stephen King's It, the eponymous menace is a being that preys on, and by unknown mechanism, manifests his victims' worst fears. When in the presence of multiple other beings, It takes the form of a clown, suggesting that the clown is the "lowest common denominator" for the irrational fears of all the protagonists.
It is also argued that notorious clown figures in literature (Pennywise in It) and real life (John Wayne Gacy) have contributed to adults being averse to clowns. Additionally, the fact that much clown behavior is "transgressive" (anti-social behavior) can create feelings of unease. 
- Quinion, Michael, "coulrophobia", World Wide Words, retrieved 14 March 2011
- Robertson, John G. (2003). An Excess of Phobias and Manias. Senior Scribe Publications. ISBN 978-0-9630919-3-2.
- Stevenson, Angus, ed. (2010), "coulrophobia noun" ((subscription or UK public library membership required)), Oxford Dictionary of English (online ed.), Oxford University Press, retrieved 14 March 2011
- Crosswell, Julia, "clown" ((subscription or UK public library membership required)), Oxford Dictionary of Word Origins (online ed.), Oxford University Press, retrieved 14 February 2011
- Harper, Douglas. "coulrophobia". Online Etymology Dictionary.
- "Trinity.edu". Trinity.edu. Retrieved 2011-07-05.
- "Why Are Some People Afraid Of Clowns?". Zidbits. 2011-10-20.
- "Health | Hospital clown images 'too scary'". BBC News. 2008-01-15. Retrieved 2011-07-05.
- Finlo Rohrer (2008-01-16). "Why are clowns scary?". BBC News.
- Diver, Mike (2006-07-10). "''DON'T send in the clowns: Bestival cancels fancy dress event''". Drownedinsound.com. Retrieved 2011-07-05.
- "''Zombieland'' review". DeccanHerald.com. Retrieved 2011-07-05.
- "''Boo! (a.k.a. I'm With Her)''". TV.com. Retrieved 2011-07-05.
- Kirkland, Mark (2004). The Simpsons The Complete Fourth Season DVD commentary for the episode "Lisa's First Word" (DVD). 20th Century Fox.
- "Some pop culture creations demonize the red-nosed men". Atlanta Journal-Constitution. 2007-02-15. Retrieved 2008-01-19.
- Fear of clowns, yes it's real NPR, August 6, 2013