the.com/gnawer

Anything that wins by a thousand tiny bites instead of one big bite.

means A person or thing that destroys, erodes, or wears something down through persistent small nibbling rather than a single decisive blow.

from Straightforward agent-noun built from the verb 'gnaw' plus the suffix '-er' ('one who does the action'). 'Gnaw' itself traces back through Old English 'gnagan' to a much older Germanic root meaning to bite or chew persistently — the same ancient family that gave Dutch 'knagen' and German 'nagen.' The word has always carried that image of small, repeated bites rather than one crushing one — think of a rodent working steadily at a bone or a beam, which is why rodents are still called 'gnawing animals' in older natural-history writing.

literal use
rodent defined by its need to gnaw
etymology
old english gnagan, to bite persistently
figurative use
describes doubt or guilt that erodes slowly
dental fact
rodent incisors never stop growing, forcing constant gnawing
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