Quote Originally Posted by Caradoc
...there were no such people as "the Vikings"; a man might go in viking (to calque a little Old Norse) one year, and the next year return to the same location as a peaceful trader. The implication, then, is that "viking" is the name of an activity, even if not literally derived qua gerund from a verb.
So, when the Normans invaded in 1066, they were viking(s).