Leo was of Syrian origin, his original name was Konon, was born in Germanikeia in the Syrian province of Commagene (modern Kahramanmaraş in Turkey). Some, including the Byzantine chronicler Theophanes, have claimed that Konon's family had been resettled in Thrace, where he entered the service of Emperor Justinian II, when the latter was advancing on Constantinople with an army of loyalist followers, and horsemen provided by Tervel of Bulgaria in 705. Leo was fluent in Arabic, possibly as a native language, and was described by Theophanes as "the Saracen minded."