Rebais has historically been attested in Latin as Rebascis in 635/636 and Rebascum in 1214. The toponym Rebais is of Germanic origin, deriving from a High German dialect, ultimately from Proto-West-Germanic *hross. The Germanic hydronym *-bak(i) entered the French language via High German, and took on two forms: the Germanic form -bach and Romantic -bais.[3]