Usually "Danes", or the "pagans"[note], or possibly the "Northmen" - though the last was more of a Continental usage.
In Francia these Scandinavians were called 'Northmen' or 'Danes' (in translation), and in England they were called 'Danes' or 'pagans' in contemporary chronicles.
Brink, Stefan. "Who were the Vikings?" Brink, Stefan, and Neil Price, eds The Viking World, Routledge: 2008.
While the word "viking" is possibly attested to in Old English (wicing), the meaning and etymology are disputed. It fell out of use during the High Middle Ages, and did not acquire it's modern meaning until it was re-introduced into English in the 18th century.
The precise meaning and origin of the word 'Viking' is, however, uncertain . . . Whatever its origins, though, it is important to realize that the word was only really popularized during the nineteenth century, and that contemporaries of the Vikings usually called them other names.
Holman, Katherine. The Northern Conquest: Vikings in Britain and Ireland Signal Books, 2007.
Note: Not meant to be taken literally - this is just what they would've meant. The actual word pagan came from Latin, and replaced the native heathen in Middle English.