Once upon a terribly long time ago, there was a tribe called the Franks. They invaded Gaul and Gaul became Franc[k]e.
They oppressed the native Gauls horribly, forcing them to eat garlic and listen to Johnny Hallyday records. Only the Franks were free. Thus they were enfranchised. They were able to speak freely, or frankly, and everybody else was disenfranchised and not able to approve things just by franking them.
How did the Franks get to France? Well, on the way they had to cross the river Main. This was easily done: they found a ford by which to ford it. The place became known as Frank-ford on the Main, or Frankfurt am Main.
Frankfurt is now best known as a financial centre, but also makes lots of low-rent sausages called Frankfurters. By the same token a hamburger comes from Hamburg* and involves no ham (or in the case of McDonalds no detectable meat at all). Also a berliner is a kind of doughnut from Berlin, which made JFK's famous remark - 'I am a Berliner' - a trifle amusing to German audiences (that is, until they elected Chancellor Cabbage).
In France the big export used to be incense, which therefore became known as frankincense, and at least one of the Franks managed to cross the Atlantic still bearing his name of "Son of the South freeborn landowner", which translates to Benjamin Franklin.