What is "heruli"

The Heruli was an auxilia palatina unit of the Late Roman army, active between the 4th and the 5th century. It was composed of 500 soldiers and was the heir of those ethnic groups that were initially used as auxiliary units of the Roman army and later integrated in the Roman Empire after the Constitutio Antoniniana. Their name was derived from the people of the Heruli. In the sources they are usually recorded together with the Batavi, and it is probable the two units fought together. At the beginning of the 5th century two related units are attested, the Heruli seniores in the West and the Heruli iuniores in the East.