The Spanish word 'demás' meaning 'others' or 'the rest' comes from combining two Latin words: 'de' meaning 'of/from' and 'magis' meaning 'more'. The combination of these elements evolved to express the concept of 'the rest' or 'others' in Spanish, essentially referring to what remains or what is additional beyond what has been mentioned.

A simpler related Spanish word is 'más' (meaning 'more'), which comes directly from Latin 'magis'. You can see this connection clearly as 'demás' essentially adds the prefix 'de-' to 'más'. Another related word is 'además' meaning 'furthermore' or 'moreover', which combines 'a-' with 'demás'.

While there aren't direct English cognates from the Latin 'magis', English speakers might recognize the root in words like 'master' and 'magistrate', which ultimately come from the same Latin root meaning 'more' or 'greater'. The Latin 'de' is familiar in many English words like 'descend', 'derive', and 'depend'.