Green’s Dictionary of Slang

duff v.1

[duff adj.]

1. [late 18C–19C] to sell ordinary goods that are touted as smuggled contraband.

2. [mid-19C] to make old goods look like new.

3. [mid-19C] (also doff) to make poor quality new goods look old, and thus of better quality; thus duffing n., duffer n. a person who does such a thing.

4. [mid-19C+] (Aus.) to steal (cattle or horses); thus duffing n.

5. [mid-19C+] (Aus.) to alter the brands on (stolen) cattle; thus duffing n. and adj.

6. [late 19C] (UK und.) to pass off a worthless article as something valuable.

7. [late 19C+] to blunder, to make a mess of.

8. [1900s–10s] (Aus.) in weakened use, to use (a possession, a place) without the owner’s permission; spec. to pasture cattle on someone else’s land.

9. [1940s] to smuggle.

10. see duff up v.

In compounds

duffing-yard (n.)

[late 19C] (Aus.) an isolated place where cattle-stealers can hide rustled cattle, rebrand them etc.