“There are various accounts of who invented the harmonica. One candidate is Christian Friedrich Buschmann, an instrument maker from Berlin.

In 1821, when Buschmann was 16 years old, he created a flute with an iron reed for tuning organs, and he apparently showed off his invention wherever he went by playing melodies on it. It is said that various people tried their hand at altering the structure of this flute, which gradually took the form of today’s harmonica.

The harmonica was first imported to Japan from Germany in 1896. At the time, it was referred to as a “Western transverse flute.” Later, the instrument was known by such names as the “mouth organ” and the “mouth harp.” Around 1900, the modern term, “harmonica” gained currency.

Actually, when German people say the word “Harmonica,” they apparently could be referring either what they call a harmonica in Japan or an accordion. The accordion, which produces sound by pushing and pulling air through bellows, is another type of reed instrument.”

Source: https://www.yamaha.com/en/musical_instrument_guide/harmonica/structure/