The Spanish word 'efemérides' comes from the Latin word 'ephemeris', which in turn was borrowed from the Ancient Greek 'ἐφημερίς' (ephemeris). In Ancient Greek, this word meant 'diary' or 'daily record'. The meaning has remained remarkably consistent throughout its evolution, as the Spanish word 'efemérides' refers to a calendar of daily events or a record of notable historical events organized by their dates of occurrence.

While 'efemérides' is a somewhat specialized term in Spanish, it's worth noting that the related adjective 'efímero' (meaning 'ephemeral' or 'short-lived') comes from the same Greek root. Both words share the concept of something related to time or daily occurrence.

English speakers might recognize this word's connection to 'ephemeral' and 'ephemeris'. An 'ephemeris' in English (plural: ephemerides) is a table giving the calculated positions of celestial bodies for each day of a given time period - essentially a celestial diary. 'Ephemeral' means lasting for a very short time, maintaining the connection to the daily or temporary nature implied by the original Greek word.