You've misunderstood something. Jeremiah's name isn't Hargrave Jeremiah. His name his Jeremiah Gottwald, and they were saying Margrave (which is a title) Jeremiah.
Margrave was originally the medieval title for the military commander assigned to maintain the defence of one of the border provinces of the Holy Roman Empire or a kingdom. That position became hereditary in certain feudal families in the Empire and the title came to be borne by rulers of some Imperial principalities until the abolition of the Empire in 1806. Thereafter, those domains were absorbed into larger realms or the titleholders adopted titles indicative of full sovereignty.
Do not listen to the haters, I repeat do not listen to the haters. This anime is easily top 5 animes in english. Its so good that you cant just watch it once.