The Domesday Book was called that because it was a comprehensive survey of England and Wales that was carried out in 1086 by order of William the Conqueror. The survey was so thorough that it was said to be as complete as the Last Judgment (Domesday), which is the day when all souls will be judged by God according to their deeds on Earth.
Who named it the Domesday Book?
The name "Domesday Book" was first used in the 12th century by the chronicler Richard of Ely. Richard used the name to describe the book because he believed that it contained all the information that would be needed on the Day of Judgment.