'RNs' originates from English, specifically the phrase 'registered nurse', where 'register' meant 'to record' and 'nurse' meant 'a person who nourishes or cares for'.

'registered nurse' developed from the combination of 'register' (from Medieval Latin 'registrare', related to records) and 'nurse' (from Old French 'nourrice', from Latin 'nutricia'); the abbreviation 'RN' and its plural 'RNs' arose in modern English as a short form for the phrase.

Initially, 'nurse' referred broadly to someone who nourishes or cares for (often a child), but over time 'registered nurse' came to mean a professionally trained and officially registered medical caregiver; 'RN' and 'RNs' now denote that professional status.