Gamut, or gamma, is the third letter in the ancient Greek alphabet. In very early times, gamma was the symbol used to represent the first note in the musical scale. Later, it came to refer to the entire scale, and that’s how Hortensio and Bianca are using it here. Today, we use gamut in a more broader sense, to refer to the full range of anything, in expressions such as “the full gamut” of something.