... Now, in place of Ursula et Undecimilla it would have been easy to read Ursula et Undecimillia ("eleven thousand"), whence the legend of eleven thousand virgins could have arisen.  As letters were never doubled in writing, the error is easily explained; it becomes altogether probable if the story of the martyr Ursula was handed down by tradition.  It would suffice that the narrator, or even the writer, was ignorant of this name of Undecimilla, which was perhaps very rare, and so transformed it into undecimillia... (Curiosities of Popular Customs and of Rites, Ceremonies, Observances, and Miscellaneous Antiquities, Walsh, 1897)