'apostle' originates from Greek, specifically the word 'apóstolos', where 'apo-' meant 'away' and 'stéllō' (or related root) meant 'to send'.

'apostle' changed from the Late Latin/Greek form 'apostolus' into Old French forms and Middle English (e.g. Old French 'apostol' / Middle English 'apostel'), eventually becoming the modern English 'apostle'.

Initially, it meant 'one sent' or 'messenger' and later took on a specifically Christian sense of 'one of the twelve disciples' and then broadened to mean 'a leading advocate or missionary' in general.