An Etymological Dictionary of the German Language/weh
weh, interj., ‘woe! alas!’ from the equiv. MidHG. and OHG. wê; corresponding to Goth. wai, AS. wâ, E. woe. From the Teut. interj. wai is derived the equiv. Ital. and Span. guai (Fr. ouais). As in the case of Lat. vae (Gr. οἷ), weh is to be regarded as an instinctive sound. The subst. Weh, n., ‘plaint, misery, woe,’ seems to be based on the interj.; comp. OSax., OHG., and MidHG. wê (gen. wêwes), and OHG. wêwo, m., wêva, f., ‘woe, pain, sorrow,’ and the borrowed Ital. guajo, ‘sorrow.’ See weinen and wenig.