It is now believed that the actual name of the historic figure Ivaylo was Vulo (wolf). There was a fragment in a historic text that described something that happened "in the time of [someone] and Vulo". Since "and Vulo" is "i Vulo" in Bulgarian, the historians misread the name as "Ivulo". "Ivulo" has since developed into the contemporary "Ivaylo". [noted -ed]