'Baptistic' originates from the English noun 'Baptist' combined with the adjectival suffix '-ic' (ultimately from Greek '-ikos' via Latin '-icus'); 'Baptist' itself derives from Greek 'baptistēs' (βαπτιστής) and Greek verb 'baptizein' (βαπτίζειν), where 'baptizein' meant 'to dip, immerse'.

'Baptistic' was formed in modern English by adding the suffix '-ic' to 'Baptist' (a term borrowed into English from Church Latin/Greek through Middle English); the root 'baptizein' passed into Late Greek as 'baptistēs', into Latin as 'baptista', then into Middle English as 'Baptist', and was later used to form the adjective 'Baptistic'.

Initially the root referred specifically to the act of dipping or immersing ('to dip, immerse'); over time the related English terms came to denote both practices (baptism) and the group characterized by those practices (the Baptists), so 'Baptistic' now means 'relating to baptism' or 'relating to the Baptist denomination'.