Online language learning resource Babbel.com has published a feature on the influence of the Old Norse lexicon, most famous as the language of the vikings, on Modern English. From the article:
Thanks to the cross-cultural fermentation that occured [sic] in the Danelaw – and later when England was temporarily absorbed into Canute the Great’s North Sea Kingdom – the English language is much closer to that of its Scandinavian neighbors than many acknowledge. By the time that the Norman conquest brought the irreversible influence of French, Old English had already been transformed beyond its Anglo-Saxon roots.
The article goes on to list 139 words from Old Norse found in modern English, from names for days and animals to words regarding war, violence, society, and culture. Also, cake.