mutton [ME] A word that came from French but which is probably Celtic in origin and related to Scottish Gaelic mult and Welsh mollt. Mutton is technically the meat of sheep more than a year old. The insult mutton dressed as lamb [E19th] describes an older person dressed in a style suitable for somebody much younger, playing on the sense of ‘dressed’ for prepared food. There is a long tradition of using mutton of women in a derogatory way. It was used as a slang term for prostitutes from the early 16th century, and the phrase to hawk your mutton meant ‘to flaunt your sexual attractiveness’ or, of a prostitute, ‘to solicit for clients’. Muttonhead was used as a term for a stupid person of either sex from the beginning of the 19th century, and this is probably the source of mutt [L19th] for both a stupid person and a dog. See also beef.