Spoiler:

some theories around were based on real life references, this will be one of them. Its not mine though, its my friends at local one piece forum. His username is BonneySHP11st, so all the credits goes to him.





So,



In Indonesians history there was once stood a hindu kingdom named The Kingdom of Kediri. The kingdom was pretty known here, particularly because we study about it in high school.



Apparently, the kingdom has some paralel similarites with the ancient kingdom in One Piece. Here they are :



1. The kingdom ruled over the eastern javanese from AD 1042 to 1222. It reached its golden age from AD1130-1160 under the reign of its most known king. <- AD 1130 - 1160. thats approximately 900-800 years ago.



2.The kingdom was remarkable for its well-known prophecy. It basically predicted the downfall of the kingdom, as well as the downfall of Indonesians archipelago to white and yellow race foreigners, then be glorious once again. The prophecy turned out to be true. <- not sure about this, but I think you can relate it to the promised day and shyarlys prediction.



3.They left out 3 historical epigraphs, mainly tell about a big war beetween Pandawa and Kurawa clans <- you can relate it to poneglyphs and the war between the AK and 20 kingdoms





Despite the similaraities, they could be mere coincidence. I mean, its not like Kediri was the only kingdom in the world which ruled around that time, nor its the only kingdom that left out epigraphs and prophecy. The similarities were not really that convincing either





However, the name of its most known king, its the one that strike me the most. His name was King Joyoboyo.





when you first heard about Joy Boy did it ring any bell for you? I bet it didnt. I mean, did the name sound so random, lol.(There was a thought about Joy Boy being an okama name but that couldnt be serious.)



Reference wise, I didnt recall anyone managed to find a real person named Joy Boy or anything close to that who might be related well, until my friend posted this theory.





Kediri and king Joyoboyo have been quite known here, though I believe very few foreigners know about it. However Oda is genius and unexpectable when it comes to using reference, so this might be plausible.





P.S : you can find informations about Joyoboyo on wiki





all credits to BonneySHP11st kaskus.