Île du Diable, or, in English, "Devil's Island", was a famous french prison up until the 50s (it's now used for satellite launch now, but whatever). It had notoriously harsh treatments of all prisoners, only one documented escape (by an anarchist, which probably describes pirates of the One Piece world even better than the revolutionaries, who likely want to instate a different government), it shares the initials ID, and there is a devil theme to a great many of the Gaol's workers, including the warden.
Sorry if this has been posted before, but I couldn't find it documented anywhere, and I also hadn't heard anyone mention it before.
(I only stumbled on it while googling for prisons that have been famous after reading the biography of Charles Manson on wikipedia and realizing that I had never even heard of the prison he's still kept in)
Interesting. You might be right. Oda probably was influenced by Dante's inferno as well.
And that anarchist's name was Duval, lol.
as if that could be a random coincidence ^^