The action or process of making something deeper, or a place that becomes deeper.
From 'deep' (verb form, meaning to make deep) + '-ing' suffix. The verb 'deep' is archaic but appears in Middle English texts referring to digging or excavation.
Medieval ditch-diggers and dredgers used this term to describe their work—the 'deeping' of rivers and moats made them more effective barriers and waterways.
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