What Is the Origin of the Saying "To Plumb the Depths"?
To plumb the depths means to let someone or yourself down severely. It also means to explore intensely. This saying has a nautical origin. It derives from when a sailor would be required to lower a lead weight into the sea on a length of rope to determine the depth of the water. In doing so, he would be required to lower the weight to the very bottom of the sea. You are perceived as being as low as the lead weight when you let someone (or yourself) down badly. Also, extending the rope all the way to the bottom means that you have kept going until you have your answer, and this is why to plumb the depths also means to explore intensely.
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