Plural of fettle or third person singular verb; multiple instances of good condition, or the action of cleaning/repairing something.
Regular pluralization and verb conjugation of 'fettle,' maintaining the base etymology from Old English 'fetel.'
What's fascinating is that 'fettles' is one of those words that sounds completely made-up in American English but sounds perfectly natural in British English—regional vocabulary differences show how English really is multiple languages!
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