Sayyiduna Abdullah al-Muzani (may Allah be pleased with him) narrated that the Messenger of Allah (peace and blessings be upon him) said: "Do not let the Bedouins prevail over you regarding the name of the Maghrib prayer." Then he (peace and blessings be upon him) said: "The Bedouins call it (Maghrib) Isha."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 1736