The documentary series London Next Stop makes a reference to Wapping and whoppers: The female narrator said that the area was called Wopping or Wapping because bodies would be fished out of the river at that location rather bloated hence the Whopper name for big burgers.

Seems an extremely unlikely explanation to me. The only part I can accept is that bodies in the water for a while get bloated and are not a pretty sight.
More likely it is simoly the narrator telling whoppers.