Claim: The horses in Young Frankenstein neigh every time Frau Blucher's name is spoken because "blucher" is the German word for "glue."
And did you know why the horses [in Young Frankenstein] whinny every time they hear the name of Frau Blucher, played by Cloris Leachman? Her name sounds like the German word for glue.
Origins:Young Frankenstein (1974) is Mel Brooks' inspired spoof of horror movies, in which Dr. Frankenstein's grandson, Dr. Friedrich von Frankenstein (Gene Wilder), inherits his grandfather's castle and begins his own attempts at creating a human being and infusing it with the spark of life. The hilariously parodical scenes which follow include the monster's encounter
with a lonely, blind hermit (Gene Hackman) who befriends him, spills hot soup in his lap, and proffers a cigar but lights the monster's thumb instead, and the dancing duet to "Puttin' on the Ritz" performed by Friedrich and his monster.
Among the cast of characters Friedrich discovers when he returns to Transylvania with his fiancée (Madeline Kahn) are a pretty assistant named Inga (Teri Garr), the bug-eyed hunchback Igor — who insists his name is pronounced "eye-gor" (Marty Feldman), and the old housekeeper Frau Blucher (Cloris Leachman). Friedrich's encounter with Frau Blucher leads into one of the film's running gags: Every time a character speaks the housekeeper's name, nearby horses whinny and neigh. A generation of film-goers, missing the obvious humor behind the gag, are now convinced they know the subtle "secret" that makes this "in-joke" funny: "Blucher" is the German (or Yiddish) word for "glue," and so the horses react in distress whenever they hear the name (because glue is made from horses, ya know).
The only in-joke connected with this gag is that so many people have missed its real humor and instead been taken in by a leg-pull. "Blucher" is not the German word for "glue," nor does it sound remotely like any German word for "glue" — standard, slang, archaic, or otherwise. Blucher (or Blücher) is simply an ordinary Germanic surname. The joke employed in the film is a take-off on the hoary melodramatic
film device of inserting an ominous organ riff or clap of thunder and having actors react with visible fright whenever the villain appears on-screen or a character refers to something evil or threatening. (Indeed, an ominous flash of lightning and clap of thunder accompanies Friedrich's first encounters with both Igor and Frau Blucher.) The "horse" bit is funny because the Frau Blucher character is neither evil nor a villain (but a disagreeable-looking harridan), because the horses are scared by the mere mention of Frau Blucher's name but are undisturbed by her physical presence, and because the gag is used ridiculously often throughout Young Frankenstein. (Horses are heard whinnying at any repetition of the words "Frau Blucher," even in settings — such as the interior of Frankenstein's castle — where no horses are present!) The second point is what seems to have thrown many viewers: The horses are terrified at hearing the name "Frau Blucher," but Frau Blucher herself doesn't bother them at all. Apparently some people have taken this bit of humor too literally and assumed the joke must have something to do with the name itself.
For some of us, the desire to believe we've been let in on a piece of secret knowledge can overpower our good sense and lead us to ludicrously arcane readings of the straightforward. Full appreciation of Young Frankenstein's broad humor requires only a familiarity with some common cinematic devices, not the process by which glue is made.