An Etymological Dictionary of the German Language/Annotated/lasch

by Friedrich Kluge

lasch, adjective, ‘slack,’ from Middle High German and Old High German *lasc; compare Old Icelandic lǫskr (Gothic *lasqs-), adjective, ‘slack, weary’; formed with a suffix sk from the root laß, lassen (Gothic *lasqa- would represent *latsqa-). Yet it is not improbable, since lasch is first recorded in Modern High German, that the root was borrowed from a Romance class similar in sound (compare French lâche, Italian lasco,‘idle’).