I. ˈdəf noun
Etymology: English dialect, alteration of dough
Date: 1816
1. : a boiled or steamed pudding often containing dried fruit
2. : the partly decayed organic matter on the forest floor
3. : fine coal : slack
II. noun
Etymology: origin unknown
Date: circa 1888
: buttocks
get off your duff
III. adjective
Etymology: duff, noun, something worthless, from duff (I)
Date: circa 1889
British : inferior , worthless