It is still not known what exactly D means. However, it is revealed that there is something that called Will of the D.. In Arabasta, Robin mentioned that all people she have known with D. in their names have strong will powers. Also, Dr. Kureha mensioned The Will of the D. and that it still lives talking about luffy. Others say that the people who have D. are somehow related as stated by Saul that all his family has it.
- People who are currently known with D. in their names: