The story
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: A liquid byproduct from a grain distillery, consisting of the liquid portion of draff after the spent grain is removed, plus washings from tuns (spent wash). Over time its disposition has varied: mostly as dumped waste, sometimes sold for part of the ration for pigs and cattle, when such a market is available. Full definition →
Etymology from Wiktionary, CC BY-SA 4.0.