'filling' originates from Old English, specifically the verb 'fyllan' (to fill) combined with the suffix '-ing' used to form nouns and verbal nouns.

'filling' changed from Old English 'fylling' through Middle English forms such as 'filing' and eventually became the modern English word 'filling' by the influence of regular noun-forming '-ing'.

Initially, it meant 'the act of making full' or 'the state of being full', but over time it evolved also to mean 'the material that fills' (e.g., tooth filling, food filling).