In 1806 East Frisia (now called Oostfreesland) was annexed by the Napoleonic Kingdom of Holland and later became part of the French Empire. Most of East Frisia was renamed the Département Ems-Oriental, while a small strip of land, the Rheiderland, became part of the Dutch Département Ems-Occidental. The French Emperor Napoléon I undertook the greatest reform of Frisian society in history: He introduced mayors, where the local administration was still in the hands of autonomous groups of elders (like the Diekgreven, Kerkenolderlings etc.), introduced the Code Civil and reformed the ancient Frisian naming system by newly introducing family names in 1811. In the following years the East Frisians registered their family names, often depending on their father's name, area or (if unfree) master.