An earl is a member of the nobility. The title is Anglo-Saxon in origin, akin to the Scandinavian form jarl, and meant “chieftain”, particularly a chieftain set to rule a territory in a king's stead. In Scandinavia, it became obsolete in the Middle Ages and was replaced by duke. In later medieval Britain, it became the equivalent of the continental count (in England in the earlier period, it was more akin to a duke; in Scotland it assimilated the concept of mormaer). However, earlier in Scandinavia, jarl could also mean a sovereign prince.] For example, the rulers of several of the petty kingdoms of Norway had the title of jarl and in many cases they had no less power than their neighbours who had the title of king. Alternative names for the “Earl/Count” rank in the nobility structure are used in other countries, such as Hakushaku during the Japanese Imperial era. (source)