The diminutive form of the name, Ursula, was always more common than the root form, due to the popularity of the legend of St. Ursula and the 10,000 virgins. In England, the name was not much used before the 16th C.
Cite as: R. Le Get, J. Uckelman, S.L. Uckelman. "Ursa". In S.L. Uckelman, ed. The Dictionary of Medieval Names from European Sources, Edition 2016, no. 1. http://dmnes.org/2016/1/name/Ursa.