Not sure if there was, but to me, the balance of evidence suggests they were introduced by the Norse, since our word for buttons in irish is Cnaipe, which comes from Old Norse [Knappr, or something like that].
Toggles may have been in vogue before then, which are pieces of wood or antler with two perforations, like the buttons of a duffel coat.
Iron age cloaks in western Europe show the use of leather toggles, which are formed by cutting strips, and rolling them up upon themselves to make cylinders, and small leather tabs were left, to attach them on.
Buttons as we know them can be found in Bronze Age, or actually copper age, Ireland, and are made of jet, and shaped like cones. They have V perforations in them, where the button holes meet inside the button, and don't actually pierce the front. They seem to be absent from the Archaeological period, until they reappear in Viking contexts.
I could be dead wrong about this, I'm simply saying that, from memory, I don't recall buttons in iron Age or early medieval contexts.