However successful this product becomes (which looks doubtful given its dependence upon signatures), its irritating generic web 2.0 startup name will prevent me from ever taking it seriously.
Square has a good product name, because it's memorable, and it fits the device (it's square!) On the other hand, iZettle is neither memorable, nor makes any sense.
Square is kind of annoying because it conflicts with Squaresoft in my mind (later renamed Square/Enix after the merge), which is collaquially called Square.