The Spanish word 'jueves' (meaning 'Thursday') comes from the Latin phrase 'dies Iovis', which literally meant 'day of Jupiter'. This phrase combined two Latin words: 'dies' meaning 'day' and 'Iovis' meaning 'of Jupiter'. Over time, 'dies Iovis' evolved phonetically into modern Spanish 'jueves', following similar sound changes that affected many Latin words as they developed into Spanish.

This etymology reflects the ancient Roman practice of naming weekdays after celestial bodies. Jupiter was the king of the Roman gods and was associated with the planet Jupiter, so his day became Thursday. This naming pattern is preserved in many Romance languages, not just Spanish.

The Spanish word 'diario' meaning 'daily' or 'diary' is related to 'jueves' through the Latin word 'dies' (day). Other Spanish time-related words that share this root include 'día' (day) and 'mediodía' (noon, literally 'middle of the day').

While English 'Thursday' comes from a different etymology (it's named after Thor rather than Jupiter), there are some English words related to 'jueves' through the Latin roots. The word 'diary' comes from Latin 'dies', as do words like 'diurnal' (relating to the day) and 'meridian' (from 'meridies' meaning 'midday'). The name 'Jove', an alternative name for Jupiter, is related to the 'Iovis' part of the etymology, as are words like 'jovial' (originally meaning 'born under the planet Jupiter').