The Spanish word 'bruma' (meaning 'mist' or 'fog') comes from the Latin word 'bruma', which originally meant 'winter solstice' or 'shortest day of the year'. The Latin 'bruma' itself developed from 'brevima', which was the superlative form of the Latin adjective 'brevis' meaning 'short' - so 'brevima' literally meant 'shortest'. Over time, the association with the shortest day of the year (winter solstice) shifted to become associated with the misty, foggy weather typical of winter days in many regions.

While 'bruma' itself is a relatively common Spanish word, a related Spanish word is 'breve', which comes from the same Latin root 'brevis' meaning 'short'. You can see how both words preserved different aspects of their Latin ancestor - 'breve' kept the meaning of 'short/brief', while 'bruma' developed from the winter solstice association to mean 'mist/fog'.

English speakers might recognize the connection to words like 'brief' and 'abbreviate', which also come from Latin 'brevis'. Just as 'bruma' developed from the concept of 'shortest day' to 'winter fog', these English words maintained the core meaning of 'short' or 'shortened'. The word 'breve' in English music notation (meaning a short musical note) also shares this etymology.