7. “ Sky,” which in Old Norse, means cloud, came into English in the Middle English period (1100-1400) , replacing the Old English (600-1100) or Anglo-Saxon word “sceo,” meaning cloud. In Middle English, “sky” meant cloud first and the sky second, while “cloud,” derived from Old English “clud,” meant rock, hill, and cloud in that order. It has been only since 1400 that “sky” meant sky and “cloud” cloud.