Yes, I know this Sword knowledge already. ^^ However, during the move to the west, and the early raids into England, the Vikings took English blades as loot and came to use them often. They did actually use the earliest verison of two-handed greatswords, though they are barely recorded.
Anyway, the concept for calling them a Zwei-hander goes beyond literal historical knowledge to that of anytime a "Nord/Norse/Northmen/Norn" is used in a Medieval/Fantasy setting. They always circumvent Viking/English/Highlandic/Renaissance weapons and combat, but to fit the Viking aesthetic. The Great-swords in Skyrim and in The Elder Scrolls series are not literal historical manifestations, rather they are collaborative manifestations with weapons from all eras.
A prime Example: Eastern Oriental Weapons were in "The Elder Scrolls III: Morrowind" but not as solely Akiviri weapons, they were of Colovian(Imperial) design as well. This has been(seemingly, but nto specifically) retcon'd to be only Akivir weapons in later games, but LORE, still has those type of weapons during that era.
