Hello guys I’m gonna make a new theory on one of the greatest mysteries of One Piece, “The Will of D”.
There exist many people in the world that seem to carry this initial and some of them try to hide it and some not, but it’s obviously an important thing. Osa said in an SBS that we must read the D on Luffy’s name simply as Di and he would explain it latter what that was. But why D? What does it stand for?
Well we know that there used to exist an Ancient Kingdom 800 years ago:
As Prof. Clover told us there was this quite prosperous Kingdom called The Great Kingdom ( Kyodai na Oukoku) and the whitespread idea is that the D have a sort of relation to this kingdom by blood or fate and they are Descendants of the kingdom carrying the will of the King (and surely Emperor-King Haki is involved somehow in that).
But why the letter D? Well I believe it stands for a japanese word: Daiou! Why Daiou? Well Daiou in japanese means excatly Great King! So that D sognifies the Will of a King. But it gets even better:
D’ have been called many names Danger, Devils, Natural enemy of God by WN and Gorosei. And there is quite a famous entity in Japan known as King Enma or Enma Daiou ( 閻魔大王 ). This figure is the great king of Hell in Budhist and hindu mythology who presides over the judgement of Hell and is always delicted with red face a beard and with offical clothes and a crown with the kanji for King (王). So this goes along with the fact the D are called Devils, and Gods Natural Enemy that are Tenryubitou.
Also one more curious thing, Doffy’s brother Rosinante told him that in Marijeoa WN used to tell their children that if they don’ behave themselves the D will come to eat them up.
Well guess what 
So to conclude this short idea we have these great people like Roger and Luffy that will carry the king’s will : Gol Daiou Roger and Monkey Daiou Luffy, who are Great Kings themselves: The Pirate King!
*Theory by BlackWing
