This is a metaphor for potential. The green corn has not yet matured; similarly, the African identity in Cuba had not yet "popped" into full consciousness before slavery crushed it.
While this translation is accurate for study and comprehension, for formal academic citation, you should reference the published translation by Robert Márquez or Roberto Márquez (depending on the edition). Use this article as a guide for interpretation. el apellido nicolas guillen english translation
Not knowing his African surname means not knowing his lineage, his tribe, his history. The poem is an elegy for a specific loss but also a metaphor for the destruction of African family structures under slavery. This is a metaphor for potential
“My last name is mine, mine, mine; / but my grandparents did not give it to me — / only the conquerors did.” Not knowing his African surname means not knowing
Notice the repetition of “mine.” He claims legal ownership of the name (he uses it daily), but he rejects its legitimacy. The translation uses “conquerors” instead of “Spaniards” here to emphasize violence, not nationality.
In Cuba, café con leche is a common breakfast drink. However, Guillén famously uses "coffee with milk" as a metaphor for racial mixing (white milk + black coffee). Here, the theft of his surname haunts even the most mundane, mixed-race daily rituals.