Here’s an interesting bit of history about the harmonica. It seems that when Napoleon was digging up those old tunes in Egypt he also uncovered the instruments used to play the tunes. A mouth organ fitted with reeds, from the Reed Sea. He also discovered that many of the tomb paintings are actually illustrations of the dance steps used to accompany the music. Napoleon loved the instrument and the music and wished to share it with the rest of Europe, so he called it the Hamtrombonium, in honor of Ham, the biblical founder of Egypt, and began on his quest of spreading the joy to the rest of the world. But folks got the name confused with the Harmonica invented by Ben Franklin a few years before, and anyway Napoleon had a hard time pronouncing the hard consonants in the word Hamtrombonium. The French have what is known as a lazy tongue and try to avoid consonants, replacing them with vowels. Probably from eating snails. This is illustrated by the fact that the word Fiddle, when spoken by a Frenchman, sounds something like Violin, from which we get that word. In France snails are thought of as a venison. The dance that accompanies the music came to be known as Hambone, as depicted in the tomb paintings. Along with the music we Americans acquired these treasures from Egypt in 1803 with the Louisiana Purchase. And that is why the Harmonica is known as the French Harp.
Or it could be because you use your tongue to play it.