'prophylaxis' originates from Greek, specifically the word 'prophylaktikos' (from the verb 'prophylassein'), where 'pro-' meant 'before' and 'phylax' meant 'guard'.

'prophylaxis' changed from the Greek word 'prophylaktikos' (and the verb 'prophylassein') into Late/Medieval Latin 'prophylaxis' and was then borrowed into English as 'prophylaxis'.

Initially, it meant 'guarding beforehand; prevention', and over time it has been maintained and specialized to mean 'a measure or action to prevent disease or problems' in modern usage.