Plath's father died when she was only eight years old, but she seems to grapple with him, his legacy, and their relationship in a great many of her poems. Research from 2012 has revealed that the FBI once investigated him for having Nazi sympathies, that he encountered discrimination as a result of his birth in East Prussia, and that he may not have felt fully in favor of the United States or its involvement in World War I. The FBI ultimately described Otto Plath as "a man who makes no friends, and with whom no one is really well acquainted." One can only imagine, then, that he was not the warmest father to young Sylvia.

Otto is the "Colossus" of the poem's title, a larger-than-life personage with whom Plath feels she has to reckon, despite his absence. In fact, his death might even make her sense of his significance in her life more pronounced, as people sometimes have a way of passing into apparent legend when they die, their qualities often becoming more exaggerated in memory. Plath addresses her father directly, claiming that she can never get him "put together entirely," as though his memory is a thing she must compose and she can never quite get it right. She seems to try to make sense of him, claiming that she has tried to "dredge the silt from [his] throat" for thirty years, to get him to reveal himself to her, but it has not worked.

Plath seems to feel like a tiny "ant in mourning" that goes over and over his face, trying to "glue" it back together, a metaphor for the work she does in trying to assemble his identity in her memory. She references the Oresteia, an ancient Greek text in which Electra tries to come to terms with the death of her own father, alluding perhaps to the idea that Plath's own struggle is at least as significant and heavy with meaning. The attempt to reckon with her father's character and his memory seem to consume Plath; she describes the work she does to reconstruct him during the day as well as how her mind hovers in and around him during the night. For her, even "The sun rises under the pillar of [his] tongue." She cannot escape his influence, and her whole life—her whole world—seems to revolve around him.