By the 12th century, Coel had become attached to the "Colchester legend", which claimed he was a ruler of Colchester in Essex and the father of Saint Helena, and therefore the grandfather of Constantine the Great. The legend originated from a folk etymology indicating that Colchester was named for Coel (supposedly from "Coel" and "castrum", producing "fortress of Coel"). However, the city was actually known as "Colneceaster" until the "n" was dropped in around the 10th century; its name likely comes from the local River Colne.