In excellent health and physical condition.
This phrase emerged in the 17th century, likely referring to a fiddle being in perfect tune and working order. A well-maintained fiddle produces beautiful music and responds perfectly to the musician's touch, making it an apt metaphor for optimal physical condition. The alliteration helped the phrase stick in popular usage.
The fiddle comparison is particularly apt because both human bodies and musical instruments require regular maintenance, tuning, and care to perform at their best. What's delightful is how this phrase elevates physical fitness to an art form - being 'fit as a fiddle' suggests not just health, but a kind of harmonious perfection in how all parts work together!
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