The true significance of the title is only discovered at the end of the poem, when the dramatic monologue is placed into context and the reader realises who the duke is speaking to about his former wife. What is so chilling about the poem, however, is that the emphasis in the title is placed both on the words "my" and "last," in that the duke clearly feels ownership of his dead wife, and that this ownership is absolute. However, also, the emphasis is placed on the word "last" because not only is the duchess dead, but the duke is now looking for a new wife, as the following lines make clear:
The Count your master's known munificence
Is ample warrant that no just pretence
Of mine for dowry will be disallowed;
Though his fair daughter's self, as I avowed
At starting, is my object.
The listener to the duke's monologue is therefore revealed to be a servant from another count whose daughter the duke, who is speaking in the poem, wants to marry. The significance of the title thus raises massive questions in the mind of the reader as to why the duke sees fit to reveal the nature of his former marriage to the servant of a count whose daughter he hopes to marry. The cold-blooded way in which he casually comments upon the way in which he had his wife disposed of because she "smiled too much" is truly callous, and either introduces the reader to a psychopath or a madman. The title therefore highlights the plight of his former wife while anticipating the suffering of his future wife.