the word "stirrup" has a beautifully literal origin in old english: stīgrāp, a compound of stīgan ("to mount, to climb") and rāp ("a rope"). it meant, quite simply, "a mounting rope." this term described a looped rope used to help a rider climb onto a horse, a function that evolved into the rigid foot support we know today. the word traveled through middle english as stirop, with the second element influenced by the unrelated word "rope," before settling into its modern spelling. its anatomical use for the stapes bone, coined in the 17th century, is a direct metaphor based on the shape's resemblance to a riding stirrup.

this is a simplex word. the modern english form is a direct phonetic and orthographic descendant of its old english ancestor. it does not contain separable, meaningful morphemes in contemporary english.