An Etymological Dictionary of the German Language/Ruhe
Ruhe, f., ‘rest, repose, calm, peace,’ from the equiv. MidHG. ruowe, OHG. ruowa, f. (also MidHG. râwe, OHG. râwa, in the same sense); comp. OIc. ró, AS. rôw, f., ‘rest.’ Goth. *rôwa (with the graded form *rêwa) corresponds exactly to Gr. ἐ-ρωή, ‘desisting, ceasing, rest,’ from Aryan rôwâ; the root rô contained in these words is probably allied to ra- in ModHG. Rast; yet the East MidG. Ruge used by Luther presents a difficulty. —