I too am descended from them.
Just as many other family names were changed by either church or civic officials when a person could not read or write, such is the D'aspit de Saint-Amand name. I also believe it is partially to have a shorter name for filling out forms, partially to have a more English name, maybe to distinguish one's self from other family members...
So, according to a cousin's research, if we truly follow *our* family name backwards it would be:
St. Amant
St. Amand
de St. Amand
D'aspit de St. Amand
then in 1662, splits into a D'aspit line and a Saint-Amand line when a D'aspit man married a Saint-Amand lady
On another of my family lines, one child of a large family kept the English version of "Comeau [Comeaux]" even though the Baptismal and marriage records (in a particular time period) of several members had the "Como" which he kept. I think it was because he had the same first name as his father and perhaps this helped to distinguish them from each other. The name change on that line has remained changed to present day even though every other line went back to the Spanish spelling (addition of the 'x').
So if I compare the Como to the D'aspit, just as I am a Comeaux/Comeau, not a Como, but the Como's are my cousins.... you are a St. Amant and a D'aspit de Saint-Amand, not a D'aspit in Louisiana - you are only a D'aspit in France prior to 1662. The D'aspit's / Daspit's in Louisiana and in France (after 1662) would be your cousins, but not your direct line.
Hope this helps....