The sense ‘(metal) rusty, stained with corrosion’ is unique to Fouke ants, with the adjective normally referring to a state of the skin, now used, with a transference of sense, to the surface of metal armour or weapons. As an alternative interpretation, the adjective may also be considered a form of ruinus¹ (‘ruined, dilapidated, in a state of decay or disrepair’), which is usually used for buildings or constructions. Both interpretations are possible (albeit with a transference of sense), but the attested forms are closer to roignus than to ruinus¹. The two Fouke ants attestations may also be corruptions of the adjective *ruilous, otherwise not attested in Anglo-Norman, but related to the ruil¹ (‘rust’) word family, and present in Continental French as rouilleux (cf. Godefroy rouilleus 7,247c). However, confusion between l and gn seems unlikely.