The plural of bilge; either the lowest interior parts of ship hulls where water collects, or the foul water that accumulates there.
Plural of 'bilge,' from Middle Dutch 'bulge.' Each ship can have multiple bilge sections or pumping areas, so the plural form became essential maritime vocabulary.
Old sailing ships had to have bilge pumps working constantly to keep the ship from sinking—there's an entire crew position called a 'bilge rat' or 'bilge hand' whose job was literally to deal with this disgusting water, which shows how important this concept was to seafaring!
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