I think that Achebe's title helps to assess what one thinks of the marriage between two people. Consider that Okeke is characterized that thinking that marriage is not a private affair. He refuses to acknowledge the private and sanctified feelings that his son feels. He repudiates any notion that marriage is private and something that exists between his son and Nene. Okeke is someone who would reject the title from an initial point of view. Yet, as the story progresses, this view of marriage is not something that is continued to be accepted. Especially so in the ending when Okeke feels a sense of dread and foreboding about how he had carried himself, he comes to understand the private nature of not merely marriages, but feelings, in general. The emotions he experiences about the abandonment of his son and grandsons is something that he feels in a private way, a sort of negative analog of the feelings that his son felt. Whereas the son felt joy and happiness and his marriage, Okeke realizes his own private feelings of guilt and regret at the end. In this, not merely marriage, but all emotions, are seen as privatized entities. It is here where the title gains significance in the face of Okeke's transformation.