By the end of the Old English period English underwent a strong influence of Scandinavian due to the Scandinavian conquest of the British Isles. Scandinavians belonged to the same group of peoples as Englishmen and their languages had much in common. As the result of this conquest there are about 700 borrowings from Scandinavian into English.
Scandinavians and Englishmen had the same way of life, their cultural level was the same, they had much in common in their literature therefore there were many words in these languages which were almost identical