The Spanish word 'gimnasio' traces back to Ancient Greek through Latin. It started with the Greek word 'gymnós' meaning 'naked', which might seem strange until you learn that ancient Greeks typically exercised without clothes! From this came 'gymnásion', meaning 'a place for exercise' (where people exercised in the nude). This word was borrowed into Latin as 'gymnasium', keeping its meaning as a place for physical exercise but also expanding to mean 'school'. The Spanish 'gimnasio' comes directly from this Latin word, preserving both meanings of a place for exercise (gym) and an academic institution.

Some related Spanish words include 'gimnasia' (gymnastics), 'gimnasta' (gymnast), and the adjective 'gimnástico' (gymnastic). All these words share the same Greek root and relate to physical exercise and athletic activities.

English speakers will recognize the cognate word 'gymnasium', often shortened to 'gym'. While in English we primarily use this word to refer to a place for exercise or sports, in some European countries 'gymnasium' still refers to a type of secondary school, preserving the academic meaning that developed in Latin. The word 'gymnastics' and 'gymnast' are also related English words from the same Greek root.