An Etymological Dictionary of the German Language/Annotated/froh
froh, adjective, ‘glad, joyous, happy,’ from Middle High German vrô (genitive vrôwes, vrouwes), Old High German frô (inflected form frawêr), ‘glad’; corresponding to Old Saxon frao (genitive *frawes, frahes), Middle Dutch vro, ‘glad’; a corresponding word in English is wanting. Old Icelandic frár, ‘quick, nimble,’ closely agrees in sound; with respect to the meaning, compare the analogous glatt and English glad. Thus the sensuous meaning ‘nimble’ might be taken as the starting-point. If the Scandinavian word be disregarded, ‘gracious, friendly,’ might be assumed as the primary meaning, in order to connect the word with the expressions for ‘master, lord,’ mentioned under frohn.