I'm reading James Boswell's The Life of Samuel Johnson and came across the story of the great man himself plus a couple of friends sitting in a tavern in Covent Garden at three o'clock in the morning drinking 'a bowl of that liquor called Bishop'. Bishop isn't that rare a word; it's in all my one-volume dictionaries. It's a sweet mulled wine according to the Oxford English Dictionary whose ingredients include oranges or lemons and port. The main ingredient is red wine and the resulting purplish colour is the reason that the drink is called 'bishop'.
Bishop is mentioned in Dickens' Nicholas Nickleby and The Pickwick Papers and towards the end of A Christmas Carol Scrooge looks forward to sharing a 'Christmas bowl of smoking bishop' with Bob Cratchit.
The drink was well known in the 18th and 19th centuries, although perhaps writer Fanny Burney was not familiar with it. Burney's play Edwy and Elgiva survived just one night at the Theatre Royal, Drury Lane in March 1794, despite the legendary actors John Philip Kemble and Sarah Siddons being in the title roles. The play is meant to be a tragedy but when Kemble, as Edwy, solemnly uttered the lines 'Bring in the Bishop!', the audience hooted with derisive laughter.
There are, or were, similar drinks with clerical names; cardinal is made with sweet Rhenish, or Rhein, wine and pope is made from Tokay, a sweet white wine.