the word 'ulna' is a direct borrowing from latin, where it meant 'elbow' or 'arm'. its origin is traced back to the proto-indo-european root h₂elén-, meaning 'elbow' or 'forearm'. this root also gave rise to the greek word 'ōlénē' (elbow) and old english 'eln', which evolved into the modern english 'ell', a unit of measurement based on the length of the forearm. the semantic journey is straightforward: from the general anatomical term for 'elbow' in latin, it became specialized in modern anatomical english to denote the specific bone running from the elbow to the wrist on the inner side of the forearm.

this word is a simplex loanword from latin. it does not contain separable morphemes within its modern english spelling.