AR-RASS. الرس
A word which occurs twice in the Qur’an the meaning of which is uncertain.
Surah xxv. 40: “The people of ‘Ad. and Samud, the people of the Russ.”
Surah 1. 12: “Before them the people of Noah and the follows of the Rass and Samud and Ad and Pharaoh, called time Apostles liars.”
According to the commentators al-Jalalan, it is the name of a well near Midian. Some take it to be the name of a town in Yamamah.

Based on Hughes, Dictionary of Islam