'authorly' originates from English, specifically the word 'author' plus the adjectival suffix '-ly', where 'author' ultimately comes from Latin 'auctor' meaning 'originator' or 'promoter'.

'author' came into English via Old French 'autor' from Latin 'auctor'; the modern English adjective 'authorly' is formed by adding the productive English suffix '-ly' to 'author'.

Initially connected directly to the noun sense of 'author' (i.e. 'of or relating to an author'), it has retained that basic meaning and is now used to describe qualities or styles characteristic of authors ('having an author's qualities').