https://en.wikipedia.org/wiki/Resonator_guitar
In 1928, Dopyera left National to form the Dobro Manufacturing Company with his brothers Rudy, Emile, Robert, and Louis, "Dobro" being a contraction of Dopyera Brothers' and also meaning "good" in their native Slovak language.Dobro released a competing resonator guitar with a single resonator with its concave surface uppermost, often described as bowl-shaped, under a …