Liz the Squeak, my grandfather used the word flash girl to describe a prostiitute. He was ex RN and had sailed under canvas. It seems possible that some of these songs were cleaned up a bit so as not to offend Victorian sensibilities but still retain a few words to give a hint of what they are referring to. The version of Pills of White Mercury, that my grandfather sang, called Down by the Royal Albion, would date itself after 1829, the year that the Royal Albion was built assuming that it was " The Royal Albion" that he was speaking about and not a ship of the same name. I have a friend with more knowledge of this area that I will check with to confirm.