A possible theme is the power of memory. The earth from home serves as a physical object that holds memories. It could be memories of childhood, family, or the simple joys of life in the homeland. These memories can be both positive and negative, and they can influence the character's actions and decisions in the story. For instance, the memory associated with the earth might make the character more determined to return home or it could make them more appreciative of their new life while still holding on to their past.