A waterproof sealant used to fill cracks and gaps, especially around bathtubs and windows.
From Old Northern French 'cauquer' meaning 'to trample' or 'press down,' which came from Latin 'calcare' (to tread, press with the heel). The shocking origin is that caulking was named after stomping with your feet! Medieval shipbuilders would literally trample oakum (rope fibers) and tar into the gaps between ship planks with their boots. The word preserved this image of pressing material down with force to create a seal.
Every tube of bathroom caulk gets its name from medieval sailors who sealed ship hulls by stomping on rope fibers with their boots. The word 'caulk' literally means 'to trample down' — so when you're sealing your shower, you're linguistically doing what sailors did with their feet centuries ago to keep their ships from sinking.
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