The term Ennen derives from the phrase '詩歌管弦者遐齢延年方也' included in "Teikin Orai," a book in the Muromachi period (it is said to have been written by Gene but unclear).
延年の語は、室町時代の書『庭訓往来』（ていきんおうらい、玄恵作と言われているが不明）中の「詩歌管弦者遐齢延年方也」の文による。