DCHP-1 Online
pot au beurre Cdn French, Slang, Hist. 
jail; guard-house, especially at a police post or trading post.
See also: butter tub
- 1814 (1954) [trans. from French of the Narrative of Gabriel Franchere] Behind all this is . . . a jail, not less necessary than the rest. The voyageurs give it the name of pot au beurre--the butter tub.]
- 1900 The voyageurs give the last [building] the name "Pot au beurre."
- 1927 The "Pot au Beurre," the half-breeds called it [the Butter Vat] and its fame was known even in Montreal.
- 1954 There was, too, a jail--the pot au beurre, or buttertub, the voyageurs called it--where unruly young men cooled off after some of the worst brawls.
- 1814 (1954) [trans. from French of the Narrative of Gabriel Franchere] Behind all this is . . . a jail, not less necessary than the rest. The voyageurs give it the name of pot au beurre--the butter tub.]