俱舍論疏 12.72

12.72

論「劫減將末至說名為濁」，總釋濁名即是顯惡。居下澤穢，故名為濁，如濁水等。

On the Śāstra's text, "When the kalpic decrease approaches its end... they are said to be turbidities": Generally explaining the designation "turbidity," which is to say, revealing badness. Settling at the bottom as dregs and defilement, they are therefore called turbidities, like turbid water and so forth.