An Etymological Dictionary of the German Language/Annotated/Schloße
Schloße, feminine, ‘hail, hailstone, sleet,’ from the equivalent Middle High German slôȥe, feminine, slôȥ (masculine and neuter?); Old High German *slôȥa is wanting; compare Dutch slote (Old Saxon *slôta), Anglo-Saxon *slŷt, *slête, English sleet (Gothic *slauti- is wanting). The origin of the cognates is obscure; it is scarcely derived from the root slū̆t, ‘to lock,’ as if hail were regarded as ‘that which is bound together compared with the soft snowflakes and the streaming rain.’ —