Capable of being gnawed; suitable or possible to gnaw on.
From gnaw (Old English gnagan, to bite or scrape) plus -able suffix meaning 'capable of.' The -able suffix makes verbs into adjectives describing possibility or suitability.
The suffix -able appears in thousands of English words (readable, movable, breakable), and gnawable shows a medieval mindset—monks even categorized wood types by whether they were gnawable by rats!
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