Duc d'Auerstaedt

The title of Duc d'Auerstaedt (sometimes written Auerstädt) was created by Napoleon I, Emperor of the French, for the Marshal of France Louis Nicolas Davout in 1808 as a victory title rewarding and commemorating Davout's splendid victory at the Battle of Auerstaedt in 1806.

The title became extinct in 1853 but was then given to the descendants of one of Marshal Davout's brothers, Charles Isidore d'Avout, by an imperial edict of Napoleon III.

...
Wikipedia