What is "ampsivarii"

The Ampsivarii, sometimes referenced by modern writers as Ampsivari (a simplification not warranted by the sources), were a Germanic tribe mentioned by ancient authors.

Their homeland was originally around the middle of the river Ems, which flows into the North Sea, at the Dutch-German border. Most likely they lived between the Bructeri minores (located at the delta of the Yssel) and the Bructerii maiores that were living south of them at the end of the Ems. The name for them is supposed to be a Latin rendering of the Germanic "Ems-werer", meaning "men of the Ems". Reconstruction of the location of other tribes in the area places the Ampsivarii at the lower Ems. In fact at least two modern cities are names after the Ems there: Emden (German) and Emmen (Dutch).