Enma is the king of hell and nothing else that's common knowledge for Japanese, Enma is a god.
And the reason oda used Ifrit is that it's pretty popular to be used in Japanese fiction to name a fire spirit/demonic species/some creature/ something mythical related to fire..just to sound cool. Given how diablo was used..he used Ifrit as an upgrade. They are not thinking of any Djin or trying to fit it here. Just use it as a cool name.
He has also mentioned it. https://worstgen.alwaysdata.net/forum/threads/oda-confirms-zoro-is-sanjis-king.36012/post-3781553
And the reason oda used Ifrit is that it's pretty popular to be used in Japanese fiction to name a fire spirit/demonic species/some creature/ something mythical related to fire..just to sound cool. Given how diablo was used..he used Ifrit as an upgrade. They are not thinking of any Djin or trying to fit it here. Just use it as a cool name.
He has also mentioned it. https://worstgen.alwaysdata.net/forum/threads/oda-confirms-zoro-is-sanjis-king.36012/post-3781553