Mieszko III the Old attention of Emperor Frederick Barbarossa, who offered his help in his restoration on the Polish throne after a payment of 10,000 pieces of silver, a sum that Mieszko couldn't reunited. Finally in Pomerania, his other son-in-law Duke Bogislaw I accepted to help him. By the agency of his Pomeranian allies, Mieszko forged his links with their Polish followers, grouped around Zdzisław, Archbishop of Gniezno and in 1181 was able to conquer the eastern Greater Polish lands of Gniezno and Kalisz, which until then had been part of the Seniorate Province. Soon after, Mieszko also managed to recover western Greater Poland.
Mieszko I of Poland copying the document he made a mistake and wrote down Dagome instead of Dagomer or even Dagomir. The name Dagomir is used to this day and its construction is similar to other Polish names like for example: Władimir/Włodzimierz or Casimir/Kazimierz. The evolution of the "-mir" element to "-mierz" is due to two separate developments: first, the regular change of the vowel "i" to "(i)e" before "r", and second, the modification of the nominative case by the vocative for certain names (hence, Kazimierz replaced Kazimier based on the vocative Kazimierze). It is debatable whether the name Mieszko is a nickname formed