Translation according to P. W. Joyce:
Glenaruid in Galway ; glen of the rud or red iron-scum or mire. See vol. ii. p. 371 [reproduced below].
Iron scum. When the soil is impregnated with iron, water springing from the ground or flowing along the surface deposits a reddish mud; which also sometimes floats on the top and forms a thin, shining, metalliferous-looking scum. This rusty-looking mud or scum is sometimes used in colouring cloth, and it is known in most parts of Ireland - or was known when Irish was spoken - by the name of rod or ruide [ridda]. It got this name from its colour; for rod signifies red. This word is given in the old form rot, in Cormac's Glossary, where it stated that it signifies "everything red." It is of course cognate with Eng. red and ruddy. The word is pretty common in names, and it is easily known, for it is never much disguised by corruption. It is anglicised rud, rudda, ruddy, riddia, etc., all which forms are illustrated in the following names. Near the village of Ballyconnell in Cavan, is a lake remarkable for this kind of deposit, called Lough Rud; and there is a small pool called Lough Arudda in the county Leitrim, one mile from the north-western end of upper Lough Macnean. Moneyrod the shrubbery (or perhaps the bog) of the iron scum, is the name of a place in the parish of Duneane in Antrim; Corrarod in Cavan (cor, a round hill); Boolinrudda at the northern base of Slievecallan mountain in Clare (booly, a dairy place). Raruddy, with its old castle ruins, near Loughrea, and Cloonriddia in the parish of Killererin, both in Galway, the rath or fort, and the meadow, of the scum; the latter the same as Clonrud near Abbeyleix in Queen's County. In Bunnaruddee (bun, the end, the mouth of a stream) near Ballylongford in Kerry, there is a spa; and all the land round it is (as a person once described it to me) "covered with shiny stuff." The final g belonging to the adjective form appears - after the manner of the extreme south - in Kealariddig in the parish of Kilcrohane, west of Kenmare in Kerry - the keal or narrow marshy stream of the iron scum.