No one I've checked with knows the origin of the word coulrophobia, the term for maladaptive fear of clowns. I've searched many sources, checked with various professionals, and asked a Twitter army of more than 100,000. Even the coulro- part makes no sense in Greek (where most phobia prefixes come from) or Latin (where some originate). I've seen a number of sources speculate on the origin, but that's all it is, speculation. Guesswork. I've yet to find any book that used the word before D'Onofrio & D'Onofrio (1998). The first edition of The Encyclopedia of Phobias, Fears, and Anxieties (Doctor & Kahn, 1989), which names many phobias, makes no mention of clown phobia. The oldest available source may be a list posted on the Internet in 1995, and the man who posted it, though he understands my question, cannot answer due to a stroke he suffered. Where he found it, we might never know.
As a kid, I always loved clowns. Still do, to be honest. I never got the point of sad clowns back then because, to me, the clown was a source of mirth and good cheer. What makes me a bit sad is that the main Clown College has closed and there just aren't as many clowns as there used to be. One of my colleagues, a now-departed member of our psychology department, filled his clinical office with clown figurines because they pleased him, although I did sometimes wonder how some of his clients felt about his dozens upon dozens of little clowns around the room when they came inside for therapy.
Here, I'm looking mainly at the origin of the term coulrophobia, not the origin of the fear itself, and I feel obligated to point out that so many people who think they have a phobia do not. A person can have a strong aversion to a particular stimulus without qualifying for a mental disorder. I love clowns but I hate heights. My height aversion does not interfere with my life in any way. Keeping my office window blinds shut because I don't like the view does not impede my ability to function in life. Even though some people find clowns to be disturbing, to be sure, most of them don't have an actual phobia (Gibson, 2004; Radford, 2016). Sources which assert that coulrophobia is not a mental illness recognized by the American Psychiatric Association, however, are overstating things. Most phobias are not listed by their stimulus-specific names in that organization's 2013 Diagnostic and Statistical Manual of Mental Disorders (DSM-5), but they are subsumed under the term specific phobia (formerly known as simple phobia as late as the DSM-III-R, 1987). Many people who show some of the diagnostic criteria for a specific phobia (extreme, persistent fear of anxiety whenever exposed to a specific stimulus; reaction out of proportion to any actual danger; either active avoidance of fear stimulus or endurance of it with intense fear or anxiety) nevertheless do not show the kind of severity or suffer from resulting "clinically significant distress or impairment in social, occupational, or other important areas of functioning" (DSM-5, p. 197) to quality for a mental disorder.
In the early '80s, Loren Coleman coined the term phantom clown to discuss accounts of children reporting "individuals wearing multicolored clothes who reportedly were trying to entice school children into coming along with them," individuals who would reportedly disappear without a trace. In his engrossing book Bad Clowns, author Benjamin Radford examines a whole history of bad clowns, evil clowns, killer clowns, stalker clowns, and more - which is a shame for the sake of real clown entertainers, not that Radford created the history of people being unnerved by clowns. Last year's rash of creepy clown sightings ("the great clown scare of 2016" - Bartholomew, 2016) led to a lot of discussion on this website about why it was happening (e.g., Eberle, 2016; Geher, 2016) and why anybody might find clowns disturbing in the first place (McAndrew, 2016). For all that discussion and all those terms that have been bandied about, where did the term for the supposed phobia come from?
The coulro- prefix alone is a mystery, much less identifying who first paired it with phobia. "It's a meaningless prefix, so far as I can tell," writes Michael Gilleland (2010). "No ancient Greek word starts with κουλρο- (koulro-), and no other English word starts with coulro-." Despite sources which call it a derivation of the Greek kolon ("limb," supposedly to convey "stilt-walker" even though that would not be correct), others acknowledge that as speculative and make it clear that the etymology is unknown (Online Etymology Dictionary). Are we even sure how the coul- part should be pronounced? Is it "cool" (Merriam-Webster), "call" (Oxford, 1st), "cole" (Oxford, 2nd), or "cowl"?
When I raised this issue on Facebook, computer scientist and fellow Psychology Today blogger Jen Golbeck found through Google Books Ngram Viewer that someone apparently used the word in 1987, but it identifies no source. For all we know, that was a misspelling of something else. Then again, a misspelling could very well be where the word coulrophobia comes from. The next bump in published mentions of the term appears after the Phobia List went online in 1995. The list webpage clearly states that all terms come from reference books, but specific sources aren't identified there and, because a stroke locked that information away, no longer can be.
American Psychiatric Association (1987). Diagnostic and Statistical Manual of Mental Disorders (3rd ed., revised) (DSM-III-R). Washington, DC: American Psychiatric Association.
American Psychiatric Association (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.) (DSM-5). Washington, DC: American Psychiatric Association.
Bartholomew, R. (2016, October 7). The great clown scare of 2016. Psychology Today: https://www.psychologytoday.com/blog/its-catching/201610/the-great-clown-scare-2016.
Culbertson, F. (1995, July 17). The phobia list. The Phobia List: http://phobialist.com.
Doctor, R. M., & Kahn, A. P. (1989). The encyclopedia of phobias, fears, and anxieties. New York, NY: Facts on File.
D'Onofrio, M. A., & D'Onofrio, E. (1990). Psychiatric words and phrases. Modesto, CA: Health Professions Institute.
D'Onofrio, M. A., & D'Onofrio, E. (1998). Psychiatric words and phrases (2nd ed.). Modesto, CA: Health Professions Institute. [The first edition from 1990 did not include the term coulrophobia.]
Eberle, S. G. (2016, October 25). Creepy clowns prowl the uncanny valley. Psychology Today: https://www.psychologytoday.com/blog/play-in-mind/201610/creepy-clowns-prowl-the-uncanny-valley.
Geher, G. (2016, October 10). The psychology because the creepy clown phenomenon. Psychology Today: https://www.psychologytoday.com/blog/darwins-subterranean-world/201610/the-psychology-behind-the-creepy-clown-phenomenon.
Gibson, J. (2004, May 7). No clowning around. Time Colonist, C6.
Gilleland, M. (2010, June 18). Coulrophobia? Laudator Temporis Acti: https://laudatortemporisacti.blogspot.ca/2010/06/coulrophobia.html.
McAndrew, F. T. (2016, October 14). Why clowns creep us out. Psychology Today: https://www.psychologytoday.com/blog/out-the-ooze/201610/why-clowns-creep-us-out.
Radford, B. (2016). Bad clowns. Albuquerque, NM: University of New Mexico Press.