The first mention of the name "Arras" appeared in the 12th century. Some hypothesize it is a contraction of "Atrebates", a Belgic tribe of Gaul and Britain that used to inhabit the area. The name "Atrebates" could have successively evolved to become "Atrades", "Atradis", "Aras" and finally "Arras". Others believe it comes from the Celtic word "Ar", meaning 'running water', as the Scarpe river flows through Arras or simply the name of Abraham's wife Sarra spelled backwards. Louis XIII reconquered Arras in 1640; the town officially became part of France in 1659.