Green’s Dictionary of Slang

tubster n.

[tub n.1 (2) + sfx -ster]

a parson.

[UK]T. Brown Amusements Serious and Comical in Works (1744) III 68: He (says the tubster) that would be rich according to the practice of this wicked age must play the thief or the cheat.
[UK]Humours of a Coffee-House 25 June 7: Don’t tell me of your Journeymen Jesuits [...] sent over to distract us, as Jo. J---bs, that Raking Draper-Trooper, and now Whisking Tubster has already done.