The origins of the English slang term “come a cropper,” in reference to taking a bad fall, are quite fascinating. Originally, this term was used to discuss a physical fall, specifically from a horse, and over time it was expanded to refer to metaphorical falls. Thus you might hear “Dave tried to climb the pub stairs and came a cropper” or “the defense really came a cropper when they brought out that witness.” This phrase is used primarily in England, and speakers of English in other regions of the world may have difficulty understanding it unless they are familiar with British English.
One of the interesting things about phrase origins in the mind of this wiseGEEK writer is the bizarre legends and explanations which rise up to explain common phrases. In the case of “come a cropper,” there is actually a very clear and readily available explanation, but that hasn't stopped people from coming up with an appealing legend.
The tall tale about the origins of the phrase involves Thomas Henry Cropper, a man who developed a version of the platen printing press in the mid-1800s. The story goes that over time, all platen presses were referred to as “croppers,” and that someone could “come a cropper” by getting his or her fingers stuck in the workings of the press. While trapping body parts in a press is a very real danger of printing, especially with older presses, this charming story is patently false.
In fact, “come a cropper” is derived from a term for the rear end of a horse, the section of a horse's anatomy which tends to become highly visible when a rider falls. The words “croup” and “crupper” for a horse's rear are derived from Older Norse words meaning “bump,” and when people fell from horses in the 1700s, they were said to have fallen “neck and crop.” In 1858, eight years before Cropper invented his press, the term “come a cropper” popped up in print in reference to taking a bad fall during a hunting expedition, and this slang term entered the English language.
This slang term was originally used among riders, often in derisive descriptions of fellow riders who tried to take dangerous jumps or rode horses which they could not control. Given the widespread popularity of riding and hunting in England in the 1800s, it is not terribly surprising that this equestrian term started being used more generally among speakers of British English.