From Greek 'harmonia' (fitting together) — originally applied to Franklin's glass armonica, later to the mouth-blown reed instrument.
A small, rectangular free-reed instrument played by blowing and drawing air through metal reeds mounted in a series of chambers, held against the lips.
From Latin 'harmonica,' feminine of 'harmonicus' (harmonious), from Greek 'harmonikos' (harmonious, skilled in music), from 'harmonia' (joint, agreement, harmony), from 'harmos' (a fitting, a joint), from PIE *h₂er- (to fit together). The word was first applied to Benjamin Franklin's glass armonica in 1762, then transferred to the mouth-blown free-reed instrument in the early nineteenth century. The underlying Greek concept links physical joining (fitting pieces together) with musical
The word 'harmonica' was first used for an entirely different instrument — Benjamin Franklin's glass armonica (1762), in which tuned glass bowls are rotated through water and touched with wet fingers. When the mouth-blown reed instrument appeared in the 1820s, it borrowed the name, and Franklin's instrument faded into obscurity, leaving the name to its successor.