'public address' originates from two elements: 'public' and 'address'. 'public' originates from Latin, specifically the word 'publicus', where 'publicus' meant 'of the people'. 'address' originates from Old French 'adresser' (to direct, arrange), ultimately from Latin elements 'ad-' meaning 'to' and a root related to 'directus'/'directare' meaning 'to direct or make ready'.

'public' entered English via Old French and Middle English as 'public'/'publice'. 'address' passed into Middle English from Old French 'adresser' (and forms like 'adrecer'/'addressen'), and eventually became the modern English word 'address'. The compound phrase 'public address' developed in modern English to refer both to a speech given to the public and, by extension, to the sound system used for such announcements.

Initially, 'public' meant 'of the people' and 'address' meant 'to direct or arrange/ to speak to'. Over time the combined phrase 'public address' came to mean specifically 'a speech to the public' and also 'the equipment (PA) used to make such announcements'.