Confusingly, though, there's the chance we might still not be talking about real cognates. The Old Norse víkingr can be derived from (Old Norse) vík (inlet, cove, fjord) + -ingr ('one belonging to', 'one who frequents'), or possibly even something close to Old Norse vika (sea mile), originally referring to the distance between two shifts of rowers, ultimately from the Proto-Germanic ~wîkan 'to recede' and found in the early Nordic verb ~wikan 'to turn', similar to Old Icelandic víkja 'to move, to turn', with well-attested nautical usages.

The Old English wīc, on the other hand, has an old Germanic etymology referring to 'camps', 'villages' and the like.

God knows there are a lot of inlets and fjords in Scandinavia, which incidentally were also places from where the surplus "víkingr" males surged west, possibly having adapted the term as an ethnonym by then; at least in modern Scandinavian languages cognates like 'viking' (pl. 'vikingar') are definitely associated with the geographic root 'vik' — as are innumerable surnames like Sandvik, Vikman, etc. Then again, those roving Vikings did of course build up "camps" and "settlements" wherever they went, although this perhaps sounds more likely a name someone else would give to them...

As for the difference between the Norse (ie North Germanic/Scandinavian) tribes/people and their more southern cousins (Angles, Saxons, Franks etc.) prior to and at the beginning of the Viking era, you might say the former were in fact quite clearly relatively more isolated in terms of geography, language and still-very-much-pagan culture. (And while eg Angles and Saxons did invade and settle much of Britain from current Northern German and parts of Denmark, this was already a couple of hundred years before, and a lot happened since.)