An Etymological Dictionary of the German Language/Annotated/Werg
Werg, neuter, ‘tow, oakum,’ from the equivalent Middle High German wërch, wërc (for the double form compare Storch), Old High German wërah (hh), and wërc, neuter; also Old High German âwirihhi, âwurihhi, neuter, ‘tow, stuppa.’ The Old High German and Middle High German forms of Werg are identical with those of Werf, hence the former is usually derived from the latter; this, however, does not explain the development of meaning. Old High German âwurihhi, ‘tow,’ may be connected with Werf and wirken, since it means ‘the refuse produced by work.’ Perhaps the simple word was developed from the compound.