My Gringotts currency is Diamonds, however I have MobHunting dropping Bags of Gold for money, but when it does it calls them the Gringotts currency name instead of the defined bag of gold name. See picture attached:

I believe the name is coming from Gringotts config.yml instead of the MobHunting generated BagofGoldCore.yml. (as I don't have Bags of Gold jar installed)

If you economy plugin is Gringotts then MobHunting should use the currency names from your Gringotts plugin, not from the BagOfGoldCore.yml unless you have some special configuration of MobHunting which I dont know of?