Get off your duff

What's the meaning of "get off your duff"? The context in which this phrase is used is "Get off your duff and do something about your situation."

Duff has been used to mean buttocks, backside, ass, from no later than 1837 and probably much earlier. The OED offers the suggestion that it might be related to a particular dough-pudding, that is,
"a. Dough, paste. (dial.) b. A flour pudding boiled in a bag.; a dumpling." In parts of northern England dough is, or was, pronounced duff, to rhyme with enough.
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