Duchy of Opole
The area is documented as part of the Upper Silesian Duchy of Opole of the fragmented Kingdom of Poland, since about 1163 under the rule of Duke Bolesław I the Tall. The name "Dobrosin" was first recorded in a 1279 deed; the name varied throughout the centuries ("Dobradin", "Dobrodzen", "Dobrodzin", "Dobrydzień" etc.). It was granted town rights according to Magdeburg law in 1374 by Duke Vladislaus II of Opole, who then vested it with various privileges in 1384. It remained under the rule of the local Polish dukes of the Piast dynasty, although as a fief of the Bohemian Crown from 1327, until the dissolution of the Duchy of Opole and Racibórz in 1532, when it was incorporated into the Habsburg-ruled Kingdom of Bohemia, as part of which it was owned by the Posadowski, Jarocki, Blacha and Blankowski noble families. The first mention of the German name "Guttentag" occurred in 1636, as a literal translation of the original Polish name. In 1645 along with the former Duchy of Opole and Racibórz it returned to Poland under the House of Vasa, and in 1666 it passed to Bohemia again.