The term "rare earth" is the English translation of French terre rare ( terre refers to an oxyde). It arises from the rare earth minerals from which they were first isolated, which were uncommon oxide-type minerals (earths) found in Gadolinite extracted from one mine. The rare earth are not called rare because they’re truly rare. They’re called rare because it’s very difficult to isolate these elements individually and it takes a lot of skill to do that.