Essenes were not only followers but also descendants of Essa.
Essa was the first born and beloved son of Isaac and grandson of Abraham.
From the Bible we know him as Esau, and his name was changed to Edom. (Genesis 25).
By Arabs, (in Quran) he is called Essa, while Christ is called Essa son of Mary.
Esau / Edom was the true carrier of Abrahamic religion.
Genesis 36 tells us that the first born son of Esau and Adah, the Hittite, was named Eliphaz; he was the carrier of Abrahamic religion and of the blessing.
Eliphaz was one of Job's three friends who visited him in his affliction. (The Book of Job - chapter 2). In the dialogues, he states with remarkable force of language the infinite purity and majesty of God.
Esau was the founder of the nation of Edom, and Edom was known before Christ times as Idumea.
Idumea was located between Judea and Nabataea and it's capital city was Hebron.
Esau – in Greek Esai, means “God is salvation, God is great gift”.
In Hebrew the meaning of this name is “he that acts or finishes”. (From Wikipedia)
Esau was renamed as Edom and in the second century B.C. his descendants were peacefully living in Idumea - south of Judea.
John Hyrcanus, a son of one of the Maccabee brothers, ruled Judea from 134-104 BC. He forcibly conquered Samaria and Scythopolis. "John's wars of fire and sword were marked by massacres of city populations whose only crime was that they were Greek-speaking.
The province of Idumea was also conquered by the Jews and the inhabitants of its two main cities, Adora and Mariss, were forcibly converted to Judaism or slaughtered if they refused."
The descendants of Esau, Idumeans – Essenes, converted to Judaism and were truly pious believers.