This 1969 X-rated bildungsroman starring Playboy's playmate of the year (and featuring Joan Collins, Milton Berle and George Jessel as characters named Polyester Poontang, Goodtime Eddie Filth and The Presence) has the worst movie title ever, according to readers of The Chicago Tribune. I haven't seen Hieronymus Merkin -- it's strangely absent from the Netflix cache -- but it sounds like an apt name for what appears to be a John Waters progenitor. The Tribune's runners-up are equally verbose and esoteric, but no less fitting (like To Wong Foo, Thanks for Everything, Julie Newmar).
For me, bad titling isn't about lengthy weirdness, but gross misrepresentation and a soul-sucking lack of creativity. There are plenty of movie titles worse than Hieronymus Merkin: It Could Happen to You (good movie, disastrous title), Crush (fine, if you mean "soul-crushing"), The Return of the Texas Chainsaw Massacre (features Zellweger and McConaughey, but how can a massacre "return"?), Swimfan (what the hell is a swimfan?), Honey, I Blew up the Kid (on second thought, this title is great).
You see what I mean? A title heralds the movie, and must be so judged. Can't Stop the Music might be a relentless crapfest, but the name is utterly perfect. And everyone in the blogosphere agrees about the next candidate for Best Movie Title Ever: Snakes on a Plane, starring Samuel L. Jackson battling...snakes on a plane.