Coulrophobia means an an irrational fear of clowns.
What, fear those delightful purveyors of slapstick comedy? One may as well go in terror of Santa Claus (but then a few people do that too, sad cases of Santa Claustrophobia). But clown humour has always embraced cruelty in its teasing and insulting of other clowns and members of the audience. Clowns represent anarchy, the personifications of unreason, and a force of nature out of control. Who knows what really lies behind their unchanging painted faces and outlandish costumes? These are all good enough reasons for even the strongest and most adult of us to feel unease in the presence of a clown.
Some children are terrified by them and a surprisingly large proportion of adults confess to finding them creepy and disturbing, so much so that this word for their condition has had to be invented. It’s not old — perhaps from the 1980s — and has been taken from Greek kolon, a limb, which seems strange until you find the related kolobathristes was a stilt-walker. This seems to have been the nearest its coiner could get to a suitable classical allusion, since ancient Greek didn’t have a word for a clown in our modern sense.