The English term and spelling "mulatto" is derived from the Spanish and Portuguese "mulato". It was a common term in the Southeastern United States during the era of slavery. Some sources suggest that it may derive from the Portuguese word "mula" (from the Latin "mūlus"), meaning mule, the hybrid offspring of a horse and a donkey. The Real Academia Española traces its origin to "mulo" in the sense of hybridity; originally used to refer to any mixed race person. The term is now generally considered outdated and offensive in non-Spanish-speaking countries, and was considered offensive even in the 19th century.