'vestryman' ultimately derives from the noun 'vestry' (plus 'man'). 'Vestry' came into English from Old French/Anglo-Norman 'vestrie' (Medieval Latin 'vestraria'), where the root 'vest-' traces back to Latin 'vestis' meaning 'garment' or 'vestment'.

The word 'vestry' originally referred to the room where vestments were kept; over time the term extended to mean the meeting or committee that met there. Middle English forms (e.g. 'vestry') later produced the compound 'vestryman' for a man belonging to that committee, yielding the modern English 'vestryman'.

Initially connected with the room for vestments or the garments themselves, the sense shifted to the meeting/committee associated with that room and then to an individual member of that committee; today it denotes a parish officer or committee member.