The narrator, Bento Santiago, explains the origins of his nickname. During a train journey from the city center to his home in Engenho Novo, Bento had a chance encounter with a poet who struck up a conversation with him. While the man recited his verses, Bento fell asleep, angering the poet. The following day, the poet expressed his dissatisfaction and dubbed Bento “Dom Casmurro.”

Bento clarifies the meaning of his nickname. He advises against consulting dictionaries for the term “casmurro,” asserting that it is not used in the traditional sense. Instead, he explains it describes someone who is reserved and withdrawn. Although the nickname quickly gained traction among his friends and neighbors, Bento says he doesn’t hold any resentment towards the poet and embraces it, acknowledging the poet’s role in also inadvertently providing the title for his novel.

Bento explains his motivations for writing Dom Casmurro. In rekindling memories of his youth, Bento attempts to reconcile with his past. In his old age, Bento lives alone with a servant in a faithful replica of his childhood home. The house boasts elaborate decorations and medallions bearing the names of emperors. He enjoys the tranquility within his home, which contrasts with the noise and restlessness of the world outside.