Something “duff” is a poor or worthless instance of its type: “We went to see a film, but it was a bit duff.”

Alternatively, it just doesn’t work or is broken: “This torch doesn’t work — I think the battery’s duff.”

It comes from a word meaning something soft or spongy, probably onomatopoeic (from the sound it makes when struck), but possibly from a variant of “dough,” meaning a pudding. (The latter may be the origin of the mainly American sense of “duff,” meaning the backside.) It may also have been influenced by a word “dowf” meaning dull or spiritless, tenuously connected to “deaf.”

There are other meanings whose origins are even less clear, though as likely as not, they have some of the same antecedents. To “duff someone up” is the same as to beat them up; it sounds a little less brutal and more friendly, but this isn’t much consolation to the victim.

“Up the duff” is a particularly mysterious slang term for “pregnant”; if “duff” here originally has the “pudding” meaning it might be analogous to other baking euphemisms, such as having a “bun in the oven,” but whereas the latter is decidedly twee, “up the duff” is somewhat coarse. And a “duffer” is a bumbling fool, especially someone who turns out — usually too late — to be incompetent for the job or task assigned to them.

Finally, in Irish place names “duff” represents Irish Gaelic “dubh,” meaning “black.” Thus “Owenduff” is “abhainn dubh,” meaning “black river.”

Mark Wainwright is a freelance writer living in Cambridge. Got a question about something you’ve seen or heard around the United Kingdom? E-mail us at: uknews@estripes.osd.mil