Green’s Dictionary of Slang

to sentence to the treadmill, to imprison.

1838		Dickens Oliver Twist (1966) 231: I shouldn’t have been milled, if it hadn’t been for her advice.
1879		H. Hartigan Stray Leaves (2nd ser.) 307: ‘What did they do?’ asked the colonel. ‘Milled me, sir, said Waller. [...] ‘Shopped me, sir,’ said Waller.