the ancient forms of its name are apparently related to the french word "raie" (old french "roie"), deriving from the gallo-roman "rica", from the gallic word "rica" meaning a "furrow": cf. middle gallic "rych", meaning a "groove", and old breton "rec" (modern breton "rec'h"), meaning a "tear". the word occurred throughout the gallo-roman region and is attested in low latin in the forms "riga", "rega" and "rige" (few volume 10, pp. 393–394).