Fortunato's mention of the Freemasons is my favorite pun from the Edgar Allan Poe short story, "The Cask of Amontillado." When Fortunato and Montressor make their way through the catacombs, Fortunato empties "a flagon of DeGrave," throws the bottle "upwards with a gesticulation I did not understand." Fortunato
... repeated the movement--a grotesque one.
"You do not comprehend?" he said.
"Not I," I replied.
"Then you are not of the brotherhood."
"You are not of the masons."
"Yes, yes," I said; "yes, yes."
"You? Impossible! A mason?"
"A mason," I replied.
"A sign," he said, "a sign."
"It is this," I answered, producing from beneath the folds of my roquelaire a trowel.
"You jest," he exclaimed, recoiling a few paces. "But let us proceed to the Amontillado."
Fortunato flashes a secret sign that only a member of the mysterious brotherhood of Freemasons can recognize. When he asks Montressor if he is of the brotherhood, Montressor coyly responds in the affirmative with a sign of his own, producing a trowel--a masonry tool--from his cloak. He is not a Freemason, but he is about to practice some amateur masonry with the trowel and hidden mortar within the catacombs--creating a wall that will hide his unfortunate friend forever. Flashing the trowel is Montressor's idea of a joke, and not the last one that he will play on Fortunato this day.
Poe had many plot problems with "The Cask of Amontillado." Montresor had to get Fortunato into the catacombs beneath his palazzo without anyone recognizing him as Fortunato's companion. That was just one plot problem. Another was: What are the two men going to be talking about during all the time it takes to get from the street to Montresor's palazzo, down into the wine vaults, and through the catacombs to the place where Montresor intends to chain his victim to the rock wall? Poe has to fill up space with some sort of dialogue, and he doesn't want them to be talking about the Amontillado. The reason Poe doesn't want them talking about the Amontillado is that Fortunato might ask some very awkward questions and become suspicious when Montresor couldn't, or wouldn't, answer them. After all, Fortunato is the expert. He knows more about Amontillado than Montresor. Otherwise he wouldn't be there. So Poe invents some incidental chitchat to fill up time and space. For one thing, he gives Fortunato a bad cold and a cough.
“How long have you had that cough?”
“Ugh! ugh! ugh!—ugh! ugh! ugh!—ugh! ugh! ugh!—ugh! ugh! ugh!—ugh! ugh! ugh!”
My poor friend found it impossible to reply for many minutes.
Notice how this fills up "many minutes." Poe is filling up space with such dialogue. Then there is all the talk about Montresor's coat of arms and his family motto, to which many people have attached great significance. And there is the business about the Masons. But never a word about the big cask of Amontillado! We can assume that there is another reason why Fortunato doesn't bring the subject up. He doesn't want to show too much interest in it because he is secretly planning to play another of his many dirty tricks on Montresor.
It is pretty obvious that Montresor is in a big hurry to find out if his fictitious Amontillado is genuine. This must be because he got, as he says, a "bargain" and would like to buy more if he can be sure of the quality. Fortunato is not going to all this trouble to help a friend, or to show off his connoisseurship, or to drink a glass of Amontillado in a dank catacomb full of dead men's bones. He wants to get in on the bargain. But he too has to be sure it is genuine. He doesn't have to taste Montresor's wine for that purpose. He knows there must be a ship newly arrived from Barcelona with a cargo of Amontillado. He could easily find the ship and taste the wine on board. But he doesn't want Montresor going to Luchesi if he should refuse to accompany Montresor to his palazzo immediately. Fortunato is rich. He could buy the entire cargo. Montresor knows this is what he is thinking because this would be typical of the "thousand injuries" he has already suffered.
So Fortunato can't talk very well because of his cough, and he isn't anxious to bring up the subject of the Amontillado because he doesn't want to show his strong interest in the possibility of making a lot of money. They talk about other things. One of the other things is the Masons.
Poe loved screts, puzzles and double-meanings. In this, the pun between "mason," (lower cases) meaning a person who works with brick and mortar, and Mason (upper case) the organization supposed to have originally arisen from the occupation. The trowel then, also, has a double-meaning. When Fortunato asks for a sign, that is a secret hand gesture known only to Masons, Montresor shows his sign- the trowel, the physical symbol of the trade. Fortunato is perplexed, but in his drunken state, doesn't explore further. We, the readers, have surmised what Montresor is up to, and we get a shudder of dread (or a little chuckle) over Poe's "joke." Oneo f many examples of irony in the story. Poe also likely includes this for the same reason we see the Masons in movies today- little is know about Freemasonry outside the members and we have a keen sense of mystery and curiousity about them. He wants to add to the mystery of his story. Also, perhaps, understanding that Montresor is a really creepy guy and poor stupid Fortunato is a victim, he uses the sense of dislike some may have for the Freemasons (the stereotype of secrecy, hidden wealth, extreme control and misuse of power did not originate with Dan Brown) to make him a little less sympathetic.
Poe was infatuated with the Freemasons. He even petitioned to join at one point, but he was denied admittance due to the macabre nature of his work. Additionally, the grotesque movement Fortunato makes is not recognized by Montresor. When asked for proof from Fortunato that he, Montresor, is a Mason, Montresor produces a trowel. The trowel is, in fact, a Masonic symbol (I am a Freemason, so trust me. I won't tell you the meaning, however). Thus, this gives us a clue as to the very character of Fortunato. During this time, "anybody who was anybody," so to speak, was a Mason. Fortunato is a man who wants to be admired and respected, but Poe gives us an impression that this man is nothing but a buffoon. He wants to appear to be more important that what he really is--something that he's not--a trait that leads to the very demise of his character. So, in short, the reason for including the Freemasons in this story is, in my opinion, to give the reader a closer look at the character of Fortunato. Also, this story is loaded with Masonic symbolism. It isn't obvious, but a Mason would recognize it. When I'm teaching my class, I have to bite my tongue. As tempting as it is, I won't break my oath. Hope this helps!