Trpimir I, the founder of the Trpimirović dynasty of Croatia, issued a document that contains the first known use of the name Croats. Trpimir I: Trpimir I was a duke in Croatia from around 845 until his death in 864. He is considered the founder of the Trpimirović dynasty that ruled in Croatia, with interruptions, from around 845 until 1091. Although he was formally vassal of the Frankish Emperor Lothair I, Trpimir used Frankish-Byzantine conflicts to rule on his own. March 4, 852. Wiki link