Most probably that was a language similar to the one used by the Norsemen. Nowadays the most similar one would be Icelandic as an example of isolated medieval Norwegian.
They spoke Norse, which is closest to Icelandic and Faroese.
The kashykians
I think the English started "borrowing" the words that the Vikings and French spoke.
The Vikings spoke a language consisting of words now used in some Scandinavian countries.
Armenian or Hebrew
English obviously
The Vikings spoke Norse.
The Minoans were from the island of Crete and the Myceneans were from mainland Greece and spoke an early form of the Greek language.
They only spoke in the same language.
The Rus tribe lived in what is now Russia long before the Vikings began their activities,, and they spoke a language completely unrelated to the Scandinavian languages of the Vikings.
They probably spoke variants of Old Norse. Icelandic is the closest modern language, which is quite different from Danish, Norwegian and Swedish.
English. The British version is quite similar to Australian English.