If you have French-Canadian ancestry, as I do, and have tried to trace your family tree back into Quebec or Acadia, you may have encountered difficulties with name changes. When many of the French-speaking people moved to areas where English was the predominant language, they often adopted new surnames that were often based upon their French surnames.
Some were obvious, such as the surname Leblanc being changed to White. Both words mean the same thing. Other changes were a bit more difficult for the non-French-speaking descendant to decode, such as the French name Courtemanche being Anglicized to Shortsleeve. Courtemanche apparently is a nickname derived from the French words court (meaning short) + manche (meaning sleeve).
I once met Boston newsman Joe Shortsleeve and asked him the origins of his name. I had never imagined a French-Canadian connection until he told me.
So how do you determine an ancestor’s original name? I would start first at an impressive list of English surnames and their French equivalents at the Quebec Project GenWeb at http://www.rootsweb.ancestry.com/~canqc/alias/angloabc.htm.
Note: People are people and each person had his or her own reasons for changing a name. I doubt if the list is 100% accurate but it does list the more common name changes. I am sure there must have been exceptions.