crupper
A strap on a horse's harness that passes under the tail to prevent the saddle from sliding forward. A specialized equestrian term.
When putting a saddle on a horse, don't forget to attach the crupper.
Alternate kanji spelling, also rare.
Kana spelling is the most practical modern form.
From 尻, “hindquarters,” and 繋, “tether,” with voicing of かい to がい. The name describes the strap passing around a horse’s hindquarters.