He also took advantage of this meeting to have his son Ecgferth consecrated as his colleague, and that prince subsequently signed charters as Rex Merciorum.
It goes back to the time of King Alfred, who seems to have frequently used the title rex Anglorum Saxonum or rex Angul-Saxonum.
The term Rex is said to come from a rabbit show.
The curly hair did not meet the standards for the breed, but the judges did not want to offend the king so they wrote the Latin word for king, Rex, beside the rabbits' names.
Since that time, an animal with a curly coat is often called a Rex.