Though you may not recognize it, the tune of the alphabet song is based on the tune of a very common nursery rhyme: “Twinkle, Twinkle, Little Star.”

In the 1780s, Mozart originally composed the tune as a variation on a classic French nursery rhyme “Ah! vous dirai-je, Maman” (which means “Ah! Would I tell you, mother?”).

Fifty years later, an American music publisher Charles Bradlee put the useful lyrics to that catchy tune: A, B, C, D… you know how it goes. In 1835, he copyrighted the song. The song’s legal title was “The A.B.C., a German air with variations for the flute with an easy accompaniment for the piano forte.”

Obviously, the rest is history.

Source: www.dictionary.com