Musannaf Ibn Abi Shayba 3:5698

Abu Bakr narrated to us, he said: Hatim ibn Isma'il narrated to us, from 'Abd al-Rahman ibn Harmala, that he heard Abu Salama ibn 'Abd al-Rahman saying: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Do not let the Bedouins overcome you regarding the name of your prayer, for it is indeed 'al-'Isha' (the evening prayer), and they only call it 'al-'Atama' (the darkness) because of the milking of the camels."