mule

The journey of 'mule' is one of ancient borrowing rather than native derivation. Its ultimate origin is obscure but points to a pre-Latin Mediterranean language, suggesting the animal was named by the cultures that first domesticated or traded it. Latin adopted this term as 'mulus', which passed into Old French and subsequently into Middle English. The core meaning of the hybrid pack animal has remained remarkably stable for millennia. The modern figurative senses—stubbornness and a backless shoe—are later semantic developments based on the animal's perceived character and, for the shoe, perhaps a fanciful comparison to the beast of burden.

The word 'mule' is a simplex word. It entered English from Old French 'mul', which derived from Latin 'mulus' (meaning a male mule; the female is 'mula'). The Latin term is likely a loanword from a Mediterranean substrate language, as similar words exist in other ancient languages of the region (e.g., Greek 'mylon', Mycenaean Greek 'mu-ki-jo').