The Spanish word 'reunión' (meaning 'meeting' or 'gathering') comes from combining two Latin elements: the prefix 're-' meaning 'again' or 'back', and the base word 'unio' meaning 'unity' or 'oneness'. The word literally suggests the idea of 'coming together again' or 'returning to unity', which evolved to refer to any gathering or meeting where people come together.

A simpler and very common related Spanish word is 'unión' (meaning 'union'), which comes directly from the Latin 'unio'. While 'unión' maintains the basic meaning of joining or combining, 'reunión' specifically emphasizes the act of people coming together in a meeting or gathering.

English speakers can easily relate 'reunión' to several familiar English words: 'reunion' (a gathering of people who have been separated), 'unite', and 'union'. All these words share the same Latin root 'unio'. The English word 'reunion' is particularly close in both meaning and form to the Spanish 'reunión', though the Spanish word is more broadly used for any type of meeting, not just gatherings of people who have been apart.