Summary: This phrase dates back to the 17th century, where “fit” originally meant “suitable” rather than “athletic,” and the fiddle was seen as a symbol of perfect mechanical order.
The ubiquity of this phrase often masks its musical origins. In the 1600s, the fiddle was regarded as a finely tuned instrument that required meticulous maintenance to perform correctly. To be “fit as a fiddle” meant that an individual was in a state of harmonious readiness, functioning exactly as intended. Over time, as the word “fit” evolved to describe physical health, the idiom shifted from a measure of preparedness to a testament of biological vigor.