(A). A réchauffé or cooked food done over again. In the
professional slang of English cooks a resurrection dish is still
called a dover (do over again).
When Dover and Calais meet—i.e. never.
A jack of Dover.
A “jack” is a small drinking vessel made of waxed leather, and a “jack of Dover” is a bottle of wine made up of fragments of opened
bottles. It is customary to pour the refuse into a bottle, cork it up,
and sell it as a fresh bottle. This is called dovering, a corruption of do-over, because the cork is done over with wax or resin.
“Many a jack of Dover hast thou sold.”
Chaucer: Coke's Prologue.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894