Mexican vaqueros used to sport hatbands called “galóns” on their sombreros…

Mexican vaqueros used to sport hatbands called “galóns” on their sombreros. A “10 galón” was a hat large enough to hold 10 hatbands. It is believed that American cowboys may have anglicized the word “galón” and thus, started referring to their own sombrero-inspired headgear as “10-gallon hats.”