The Spanish word 'sor' comes from the Latin word 'soror', meaning 'sister'. It evolved through Old Catalan 'sor' before entering Spanish. While the Latin 'soror' was used for any sister, the Spanish 'sor' became specialized as a religious title, specifically used to address nuns, similar to how we use 'Sister' in English when addressing female religious figures.

A related Spanish word is 'sororal', meaning 'sisterly' or 'of or relating to sisters', though this is a more formal or academic term. The more common word 'hermana' is used for 'sister' in general contexts in Spanish.

Several English words share the same Latin root 'soror'. The most obvious is 'sorority', a social organization or club for female students at a college or university. Other related English words include 'sororicide' (the killing of one's sister) and 'sororal' (relating to sisters). The word 'sister' itself, though similar in meaning, comes from a different Germanic root rather than the Latin 'soror'.