What it means
Means you’re feeling in cracking health, buzzing with energy, like nothing could knock you down. People trot it out after a rough cold clears, after a good run, or when you wake up annoyingly fresh. The fiddle bit is basically about being well tuned and working smoothly, like the instrument. Old-school, but still does the job.
Usage examples
"Nurse asked how I was after the op, and I went, fit as a fiddle, mate. Had a cuppa, took the stairs, nearly beat everyone to the ward."
"My grandfather is eighty-six and still fit as a fiddle, he walks five miles before breakfast."
"After two weeks off the booze I feel fit as a fiddle, properly back in the game."
Where it comes from
Idiom recorded in English since the 17th century. "Fit" once meant "suitable" rather than "athletic", and the well-tuned violin (fiddle) was the household image of something perfectly in order, ready to play. Over time "fit" drifted toward physical condition and the phrase came along, but the comparison to a tuned instrument still carries a flavour of crisp readiness.
Other ways to say it
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