Mid 18th century: from dialect croup 'to croak', of imitative origin.

• crop from Old English:

  From around ad 700 to the late 18th century crop, related to group (late 17th century), had a sense ‘flower head, ear of corn’, which gave rise to the main modern meaning ‘a cultivated plant grown on a large scale’ and also to senses referring to the top of something, such as the verb uses ‘to cut very short’ or ‘to bite off and eat the tops of plants’. The sense ‘a very short hairstyle’ goes back to the late 18th century but is particularly associated with the 1920s, when the Eton crop, reminiscent of the style then worn at the English public school Eton, was fashionable for young women.

  To come a cropper is to suffer a defeat or disaster. The origin of the phrase may be the 19th-century hunting slang term ‘cropper’, meaning ‘a heavy fall’. Cropper probably came from neck and crop, an expression meaning ‘completely or thoroughly’ and originally used in the context of a horse falling to the ground. Crop here referred either to the rider's whip (originally the top part of a whip) or the horse's hindquarters. This sense is found in Old French croupe ‘rump’, which appears as croup in Middle English, and is the source of the crupper (Middle English), the bit of harness that goes from the saddle under the horse's tail, and which lies behind the word croupier (early 18th century). In early use, this was a term for a person standing behind a gambler to give advice, adopted from French, cropier ‘pillion rider, rider on the croup’.

Middle English: from Old French croupe, ultimately of Germanic origin and related to crop.