The Spanish word 'hora' (meaning 'hour') comes from Latin 'hora', which in turn was borrowed from Ancient Greek 'ὥρα' (hōra). In Ancient Greek, 'ὥρα' had a broader meaning referring to any period of time or season. When the word was borrowed into Latin, its meaning became more specific, focusing primarily on the concept of an 'hour'. This meaning was then inherited by Spanish, preserving both the form and meaning from Latin almost unchanged.

Several common Spanish words are derived from 'hora', including 'horario' (schedule/timetable), 'ahora' (now), and 'horita' (diminutive meaning 'in a little while'). These words all relate to concepts of time, with 'ahora' literally developing from the phrase 'a hora' (at this hour) to mean 'now'.

English has several words related to Spanish 'hora' through the same Greek root. 'Hour' itself comes from the same source through Old French. Other related English words include 'horology' (the study of time measurement), 'horoscope' (literally 'hour-watching' in Greek), and 'horarium' (a daily schedule, especially in monasteries). The word 'hour' underwent more sound changes in English compared to Spanish 'hora', which retained a form closer to the original Latin.