Well the Dutch and Flemish people called them "Noormannen" after the "Norse" from Norway. In the Latin texts they where called "Nortmannorum".

(Edit: I should say that we only have Latin text and no "Dutch" texts about the viking invasions.)

Wich I personnaly find strange since the coasts of Flanders and 'Frisia' had primarily trade contact with the Danish as opposed to Norway. This trade contact was already established way before 800 wich is considered the start of the "viking-age"

Also the later plunder and raiding parties where mostly from Denmark.

But as is often the case the people didn't really make a distintion between the Swedish, Danish or Norse invaders from the North.

Source (Dutch): Luit van der Tuuk, Noormannen in de Lage Landen, handelaars huurlingen en heersers, 2008.