Dorsey is from the French surname d’Orsey, as in the d'Orsey Museum in
Paris (
http://www.musee-orsay.fr:8081/ORSAY/orsaygb/HTML.NSF/By+Filename/mosimple+index?OpenDocument). D’Orsey means "Of Orsey". Orsey is derived from the "ours", meaning bear (the animal) in French, and is derived from the Latin Ursus.
Hope you find my interpretation not too unbearable, pun intended.