1. Vikings didn't have horns on their helmets. The idea of it may stem from a ninth century Oseberg tapestry which features a horned helm, probably for ceremonial use. Romantic artists and nineteenth century costume designers liked the idea though and probably the greatest Viking myth was born.
2. America was not discovered by Columbus in 1492. Erik the Red's son Leif Eriksson (Leif the Lucky) got there first, discovering "Vinnland" in North America in the year 1000.
3. Many people claim that the day of the week Friday is named after Freyja but it is actually named after Frigga. Etymologically, Freyja stems from German - Frau meaning lady, whereas the English name of Friday comes from the Anglo Saxon name for Frigga - Frige ... so it is fair to contend that Friday is named after Frigga, Odin's wife. Whether or not they are actually the same goddess (Freyja being married to Odur!) is another matter!
4. Santa Claus was not invented by Coca Cola ... or Victorians! At Winter Solstice, Vikings exchanged presents and believed that the large, white haired, white bearded mystical Odin would career across the night sky in a chariot, bearing gifts!
5. Certain sources delight in sharing details of "bloodeagles" a method of torture and execution where victim's ribs were cut open and broken resembling wings and lungs extracted and pinned to the back. There is no solid evidence that anyone ever actually did this and it may be the result of a gruesomely overactive imagination of a writer at the time.
6. Many people assume that the famous turtle or tortoise brooches worn by Viking women below the shoulders suspending aprons and decorative beads from the dress are a given fact. Re-enactors are encouraged to buy them from specialist sites and society meetings are full of them. The only evidence for this comes from grave finds rather than contemporaneous pictorial evidence but they are so strongly associated with the time that Lisa wears them as Leagrid!
7. Similarly, the Viking "women's knife" (again sold by re-enactor shops and craftspeople) were found in graves but may only hold ceremonial purpose or could be intended for use in the afterlife.
8. Children sometimes suggest to us that Vikings used urine to control headlice but I can find no evidence for this and it seems highly unlikely to me. Perhaps the confusion stems from other early cultures using the technique or later ones, or the fact that lighter hair was indeed prized. A strong soap including lye was used to lighten or bleach the hair though and combs were used to control headlice. The idea of such clean people as the Norse settlers soaking their hair in wee doesn't ring true for me!
9. Vikings were not savages as they are sometimes portrayed; finds relating to cleanliness and Norse art, particularly carvings attest to this.
10. The meaning of the word Viking has not been determined for certain although some think it means pirate. People think this since it was used as a verb - to go a-Viking, which loosely translated means to go on a journey. Those initial journeys may have been largely to raid, hence the assumption. Etymologically, though, it could stem from Vik meaning creek (ie. those who come from a place of creeks or who hide in them!); but equally it could stem from Vig meaning fighting.
+ 1 extra one!
11. The famous story of the "foolish" Viking King Cnut, getting his feet wet after telling the tide not to come in is wrong too! It has been corrupted over the years and in fact he was illustrating a point to his courtiers that even a king is bound by natural laws. I like Cnut - he sounds like he had his head screwed on!