Not quite, John. The latest research (Cecil Brown's article, so recent that it is Copyright 2005!) states that Allen was only Mr. Britt's nickname. Albert was his real given name. "Frankie and Albert" thus preserves the real names of both protagonists. Frankie herself called Albert "Al," as revealed in the many interviews she did after it was discovered that the song documented a real event. So some people called him "Al Britt," others "Allen Britt," and others "Albert Britt." Albert is a pretty logical ending place for these permutations, unlike "Polly Ann" for "Margaret," "Maggie D.," etc.

Also, there is a simple explanation for why the true historical facts are not present in any version of Frankie. It's not because tradition distorts the facts beyond recognition. It's because the later songs were all based on the earlier songs, not on trial documents. The earliest song was written by the great 1890s street songwriter Bill Dooley (also responsible for the original Stack O Lee), and was already wildly inaccurate. Dooley apparently wrote it so soon after the incident that the facts of the case had not been established; according to testimony that came out at Frankie's later lawsuits against the movie versions of her stories, Dooley was already singing and selling a version of the song the night after the shooting! At that time, only Frankie (who was in jail) knew the exact sequence of events, because the shooting and the lead up to it occurred in private. Some people like Alice Pryor, Albert's parents, and Frankie's roommate Pansy Marvin would have known parts of the sequence, but only Frankie knew the whole thing until after the trial.

So Bill Dooley was guessing. He was also inventing what he thought was a good story, rather than telling the somewhat bizarre true story (which was that Albert returned home to Frankie after an evening with Alice Pryor, took out a knife, and began cutting Frankie for no apparent reason; she shot him in self-defense).

And that's exactly what I'm suggesting about names like Polly Ann. The singers/re-composers of the ballad of John Henry were guessing, making up or creating, if you prefer, the story elements they didn't know from history. There does not have to be a genetic line of some kind tying "Margaret" to "Polly Ann," because if a singer doesn't know the real name he or she will create a new one, and "Polly Ann" sounds much more like a product of that random process than like a logically-derived product of "Margaret Dabney."

I've also read Buckley's thesis, by the way. You can find the most recent article on Frankie and Albert in the collection The Rose and the Briar. I didn't like the first few articles in this book, and said so on a thread a couple of weeks ago, but the rest of the book has been quite good. John Garst's thorough inquiries into Delia's Gone are cited, too! Sadly, they did not ask John (or anyone else) to do a piece on John Henry.