The Rusins made up a significant part of the population in the Moldavian principality, which was reflected in the Moldavian medieval diplomacy. The acts of the Gospodar Chancellery contain a large number of names and nicknames of the East Slavic origin. The widely spread anthroponyms with the root rus- give evidence of the ethnic origin of their bearers. The bearers of names and nicknames with the root ruscan be met in the documents throughout the whole history of the Moldavian principality. These people were represented in all social classes. Nowadays the surname Rusu (from Rus- Russian) is the most common in the Republic of Moldova, which is part of the former Moldavian medieval principality. By the beginning of 2011, there were 23 028 people with this surname there.