His first name "Masamune" was named after the 9th lord of Date clan, Masamune DATE (Daizen no daibu [Master of the Palace Table]) who was the founder of a revival during the Muromachi period; therefore, he was often called Tojiro-Masamune to distinguish from Masamune DATE of Daizen no daibu.
諱の「政宗」は伊達家中興の祖といわれる室町時代の第9代当主・伊達政宗(大膳大夫)にあやかったもので、この大膳大夫政宗と区別するべく藤次郎政宗と呼ぶことも多い。