Do we owe it to some cnut in the Eleventh Century?
More;The introduction of the name Engla land took place in the early eleventh century after five centuries during which the land was known as Britene and to a lesser degree as Albion, names carried over from earlier times. But Britene was the geographical or territorial name for the entire island, not a country or political name.
From the later ninth to the early eleventh centuries Scandinavian invasions led to the collapse of most of the Anglo-Saxon tribal kingdoms and to the rise of Wessex as the leader of the native resistance. With this came the gradual emergence of a single people with a common culture, language, and political loyalty, and a new designation or name – the Angelcynn, the English kindred, race or people. By the end of the tenth and beginning of the eleventh centuries Angelcynn had become the dominant term in the Anglo-Saxon Chronicle.
From 1014 Angelcynn was abandoned by the author of the Chronicle. This was a moment of grave political crisis. In 1013, in the latest of a series of successful Scandinavian invasions, the Danish ruler Swein, after defeating the English monarch Aethelred who fled into exile in Normandy, occupied much of the country, and was named king of the English. Swein’s unexpected death in February 1014 led to the selection of his son Cnut as his successor and the author of the Chronicle tells how:
Then all the councillors who were on Engla londe, ecclesiastical and lay, determined to send for King Aethelred and they said that no lord was dearer to them than their natural lord if he would govern them more justly than he did before.
This is the earliest use of Engla land in the Chronicle. For the next five years the author wavered between Angelcynn and Engla land, as if in doubt as to which name was most appropriate. But in 1020 he settled on the latter and never used Angelcynn again, nor did any of the later authors of the Chronicle (with one exception, the Peterborough Chronicle annal for 1096). By now Engla land had become the standard name for the country in the Chronicle.