'convert' originates from Latin, specifically the word 'convertere', where 'con-/com-' meant 'together/with' and 'vertere' meant 'to turn'.

'convert' passed into English via Old French 'convertir' and Middle English 'convertir'/'convert', evolving into the modern English 'convert'.

Initially it meant 'to turn around' or 'to turn together', but over time it evolved to mean 'to change (something) into another form' and 'to change (one's) belief or religion'.