The interplay of Old English and Old Norse can easily become as engrossing a subject as the history of the Scandinavian invasions of England. Along with its speakers, Old Norse came to England to settle, and to stay. Because of its similarity to Old English, it is sometimes difficult to ascertain the Norse heritage of a Modern English word although, on the other hand, some forms are unmistakeable. English and Old Norse, sharing a common ancestry, differed on the pronunciation of the blend sk/sc. The Scandinavians pronounced it "sk", but the English, though they spelled it sc, pronounced it as "sh". Thus, for example, the Scandinavians had a word skelle which corresponds to our modern-day shell. The words skirt/shirt are textbook examples of this divergence; though ultimately, they were preserved as names for separate articles of clothing. Perhaps even more interesting is the passage below:
". . .Our word bloom (flower) could have come equally well from O.E. blōma or Scandinavian blōm. But the O.E. word meant an 'ingot of iron' whereas the Scandinavian word meant 'flower, bloom.' It happens that the Old English word has survived as a term in metallurgy, but it is the Old Norse word that has come down in ordinary use."
Quote from A History of the English Language by Albert C. Baugh