Puddle-dock, n. — Green’s Dictionary of Slang

Puddle-dock n.

[Puddle Dock in London, now the site of the Mermaid Theatre, but orig. a large stagnant pool off the River Thames]

Countess of Puddle-dock (n.) (also Duchess of Puddle-dock, Queen of...)

a self-appointed but spurious aristocrat.

1648		‘Mercurius Melancholicus’ The cuckoo’s-nest a [sic] Westminster 8: Marry come up mother Damnable [...] Must you be Queen? yes you shall; Queen of Puddle-Dock, or Billingsgate, that is fittest for thee.
1673		T. Shadwell Epsom Wells II i: Stinking Town! I had rather be Countess of Puddle-dock, than Queen of Sussex.
1738		Swift Polite Conversation 26: nev.: I promised to squire the Countess to her Box. miss.: The Countess of Puddledock, I suppose.