Girolamo Montesardo claimed to have invented Aflabeto, a system of notation for guitar chords and strumming in the early 17th century. Montesardo makes this claim in his book, Nuova inventione, published in Florence in 1606. Regardless of whether Montesardo invented Alfabeto, he is famous for the description of the system in Nuova inventione, which also includes popular songs (set in Alfabeto) from the time.
Montesardo was a singer and composer by trade, but didn’t write anything original for guitar (he did compose vocal works, however). An overview of the contents of Nuova inventione can be found here.