'Yes', I said, 'for the love of God!' What does Montresor mean by these words in "The Cask of Amontillado"?

It is to be noted that Fortunato does not call Montresor by name except at the end when he cries, "For the love of God, Montresor!" Poe's main purpose for writing this line was to show that Fortunato understood what was happening and who was responsible. Montresor specifies that one of the requirements for perfect revenge is that the victim know the identity of the "avenger."

A wrong is unredressed when retribution overtakes its redresser. It is equally unredressed when the avenger fails to make himself felt as such to him who has done the wrong.

Fortunato has been drunk ever since Montresor encountered him on the street, and Montresor has kept him drunk by giving him two bottles of French wine. But once Fortunato is tightly chained to the granite wall, the author wants to fulfill Montresor's specifications for redressing a wrong. Montresor explains:

I had scarcely laid the first tier of the masonry when I discovered that the intoxication of Fortunato had in a great measure worn off. The earliest indication I had of this was a low moaning cry from the depth of the recess. It was not the cry of a drunken man.

This is merely to show the reader that Fortunato understands where he is, what is happening to him, and who is responsible. Perhaps Fortunato even understands why it is happening to him. So the following exchange between victim and captor can be interpreted as intended to show that Montresor has made "himself felt as such to him who has done the wrong," as well as Montresor's expression of complete satisfaction at the success of his revenge.

"Yes," I said, "for the love of God!"

This reply probably means that Fortunato, who is begging for mercy, is well aware of his captor's identity and is saying exactly what Montresor wanted to hear him say. Montresor wanted to hear the proud, scornful man begging him for mercy. Montresor could not be there to observe what happened to his prisoner over the following days and weeks. Evidently Fortunato was in for a long, lingering death. But the action ends with

"Yes," I said, "for the love of God!"