An Etymological Dictionary of the German Language/Annotated/Klage

Klage, feminine, from the equivalent Middle High German klage, Old High German chlaga, feminine, ‘complaint,’ properly ‘a wail as an expression of pain’; wanting in all the early periods of the Old Teutonic languages except Old High German; adopted as a legal term in Modern Icelandic in the form of klögun. ModHG and Middle High German klagen, from Old High German chlagôn. The pre-Teutonic root is probably glak or glagh; yet cognates are wanting.