The “Will of D.” is a mystery surrounding some people who have the initial “D.” in their names. Let’s see the possible meanings of D.:
1 – Dawn
It’s the most obvious one, a lot of people already thought about it since the first chapter of One Piece is called Romance dawn, and a lot of character have mentioned the “Dawn of the world” as the big event that the Straw Hats are supposed to bring in to the world.
Kozuki Toki said in her prophecy that someone will bring a new dawn.
2 – Devil
This hit me recently, the D. are “the natural enemy of gods”, what is the natural enemy of God? The Devil.
In One Piece the Celestial Dragons call themselves Gods and rules by pretending through the World Government that they are the good guys that takes down the evil pirates. But we know that in reality they are doing the most evil stuff hidden in the shadows, so it seems very fair for people like that calling themselves God that the one who can take them down would be the “Devils” or “Demons”.
There have been a lot of time where Luffy has been called a Demon in One Piece, and we know he doesn’t want at all to be a hero, so him taking down the so called “Gods” by being considered the “Devil” seems really fits.
What is even more going for this possiblity is the fact that , since the D. are the ones who are supposed to bring “the Dawn of the world”, one of the equivalent word for Devil is “Lucifer” and in Latin “Lucifer” literally means “the one who brings light”.
3 – Dream/Dreamer
In my opinion this one is the most likely to be the significiance of D. Roger said before he died that the One Piece is “what every man can dream of”, and we know that the will of D. and the One Piece are completely connected.
The story of the Straw Hats is a story of people going on a journey to achieve their dreams.
In general One Piece is a story where the strongest character is the one who have the strongest will to accomplish his goal. So I think that’s what it could be the Will of D., the will of Dream, the will of the people who will do anything to accomplish their dreams. And since most of these dreams are related to freedom in some way, overthrowing this tyrannic organisation that rules the world, it’s a necessity to see these dreams come true, which is why the ones who have the Will of Dreams are the natural Enemy of Gods, because they won’t accept the natural order of the world if it’s in the way of what they want.
*Theory by boris957