The other day I picked up a paperback collection of 10 stories by Poe and noticed that there was one I've been meaning to read for several years, "Thou Art the Man." A couple of years ago I made a study of Poe's three detective short stories, a genre he created, but I hadn't gotten to this one which is sometimes also said to fall into the detective category, a story of what Poe called "ratiocination." This one is rather lightweight from a literary standpoint, especially compared to "The Purloined Letter," which I think is a masterpiece of literary perfection. The tone of "Thou Art the Man" is quite humorous and, along with its small-town Americana setting, reminded me of Mark Twain (who wrote a few detective stories himself).
Imagine my surprise when I found that one of the characters, an older gentleman who disappears and is believed (correctly) to have been murdered, is named "Barnabas." I had never come across that information in any Dark Shadows discussions or books that I can recall.
While the story bears no resemblance to "Dark Shadows," it still could be the source for Barnabas's name, unless we know that the name "Barnabas" was definitely picked up from a New England tombstone, which I think I read years ago.
"Thou Art the Man" is a rather quick read and I would recommend it as a "Saturday Evening Post" type of story and not one of Poe's masterpieces of terror. In a paragraph introducing the story in my old Scholastic copy (which somehow I had at hand), it's said that this story introduced a new aspect to detective fiction, that of the (amateur) detective narrator, a fact I had read nowhere else despite my extensive reading into the history of detective fiction.