John Gay and the Meaning of Names

In the Beggar's Opera, Gay uses many obvious surnames in order to better describe the character. Lockit being a jailer, Filch a thief. The not as blatant names I wondered about, however, were Peachum and Polly. After some digging, I was able to find that "to peach" was old slang for giving evidence against another, or to turn informant. That's rather clever on Gay's part, because it is not a readily known slang. Perhaps it was more widespread in the past, but if not it still identified Peachum and his dealings without being blatant. His thieves would not have been so quickly informed of the nature of his deceptive trade as they would have been by a prostitute named Moll or Doxy. Also, as slang is more often used by the lower-class than it would have been by the gentry, it may have been a bit of a tongue-in-cheek way to include a laugh that they not completely understand. Gay's opera, while clearly made for the rich, as they were the ones who could afford the seats, would have been just as enjoyed by the lower-class I'm sure, especially because they were the subject matter.
Polly's name was far more difficult, and I could not find anything about a hidden meaning to her character. This is rather odd, considering how just about every character Gay included had some sort of descriptive characteristic included in their name. Why simply leave Polly out? To me, the name Polly brings forth the feeling of a light, carefree, naive girl, something reminiscent of the name Daisy. However that's a personal connection, and not necessarily a tone that Gay had intended. I did find that the origin for the name Polly was  a form of Molly, which came from Mary (but also held the connotation of Moll). That in itself could be telling, if it was common knowledge that Molly and Polly were two forms of the same name. However, that still leave Polly's character ambiguous. She could be the reverse of Molly (or Moll) someone who is innocent and still believes in love and that men can be good, as her name is an altered version of Molly, or she can be cut from the same piece of cloth (derived from the same name) and be wise to the true reality of the world and going against social conventions irregardless (though hers being to marry for love, rather than to fall into an unsavory trade). It seems Gay didn't intend to give up any glimmer of insight on Polly, that I was able to find, by naming her such.