The Spanish word 'arena' comes from the Latin word 'harena' (also appearing as 'hasena' in archaic Latin), which meant 'sand' and also referred to the sand-covered floor of amphitheaters where gladiatorial contests took place. Over time, this word evolved from Latin to Spanish, maintaining both its original meaning of 'sand' and the extended meaning of a place where events or contests are held.

The word 'arena' is itself a common and fundamental Spanish word, serving as a base for other related terms like 'arenoso' (sandy), 'arenal' (sandy area or beach), and 'arenilla' (fine sand). These words all maintain the connection to the original meaning of sand.

The English word 'arena' is directly related to the Spanish 'arena', as both come from the same Latin root 'harena'. While Spanish retained both meanings of 'sand' and 'venue for events', English only kept the meaning of a place where events occur, such as a sports arena or entertainment arena. This semantic shift happened because the Romans used sand to cover the floors of their amphitheaters, and eventually, the word for the sand itself came to refer to the entire venue.