The Spanish word 'party' is a modern borrowing from English 'party', which ultimately comes from the Latin word 'pars' meaning 'part' or 'portion'. The English word evolved from referring to a portion or group of people to specifically meaning a social gathering or celebration, as well as a political group. When the word was borrowed into Spanish, it primarily took on the meaning of 'social gathering' or 'celebration', especially in the context of modern, informal parties.

Some related Spanish words that share the Latin root 'pars' include 'parte' (part), 'parcial' (partial), and 'participar' (to participate). These words all retain meanings related to the original concept of a 'portion' or 'part' of something.

The English word 'party' is obviously directly related, but other English words sharing the Latin root 'pars' include 'part', 'partial', 'participate', 'partition', and 'partner'. All these words maintain some connection to the original meaning of 'part' or 'portion', whether referring to a physical piece, a group, or involvement in something.