'functionary' originates from French, specifically the word 'fonctionnaire', where 'fonction' (from Latin 'functio') meant 'function, duty' and ultimately from Latin 'fungi' meaning 'to perform'.

'functionary' changed from the Medieval Latin word 'functionarius' and the French word 'fonctionnaire' and eventually became the modern English word 'functionary'.

Initially it meant 'one who performs a function' or 'relating to a function', but over time it evolved into its current meaning of 'an official, especially a bureaucrat or administrative officer.'