[2] It was known in Latin as Anisus or Anasus,[3][4] of uncertain origin; Anreiter et al. tried to link it to an Indo-European *on- and the hydronymic suffix *-is-.

[8] The West Slavic languages have different names for the river: in Czech it is called the Enže;[9] in Slovak, the Enža; and in Polish, the Aniza.

Between Admont and Hieflau, it takes a turn to the North and passes through the Gesäuse, a gorge of a length of 15 km (9.3 mi), where it penetrates the limestone of the Ennstaler Alpen.

In the middle of the 19th century, canals began to be built along the 70 km (43 mi) between Weißenbach and the Gesäuse, in order to make use of the water for agriculture and forestry.

[12] The power stations are listed beginning at the headwaters: The most important inflows are the Palten, the Salza and the Steyr.