Green’s Dictionary of Slang

canister n.2

[SE camis, a surplice + camesa n.]

a clergyman.

[UK]J. Ware Passing Eng. of the Victorian Era 62/2: Canister (Street). A preacher. Evidently a corruption of a street preacher whose name was something like, for instance, ‘Kynaster’, and popularly Anglicised.