'labeler' originates from English, formed by the noun 'label' (ultimately from Old French 'label' / 'labelle', from Medieval Latin 'labellum') plus the agentive suffix '-er' (from Old English/Proto-Germanic meaning 'one who').

'label' changed from Medieval Latin 'labellum' (a diminutive of Latin 'labrum') into Old French 'label'/'labelle', entered Middle English as 'label', and later the agentive suffix '-er' was added to create the modern English noun 'labeler'.

Initially the root 'labellum' referred to a 'small lip', but through Old French it came to mean a 'tag' or 'label'; over time the meaning evolved to the modern sense of a 'tag' and subsequently 'labeler' came to mean 'one who attaches labels'.