'filmy' originates from English, specifically the word 'film' + suffix '-y', where 'film' meant 'a thin skin or membrane' and '-y' meant 'characterized by or full of'.

'filmy' developed by attaching the adjectival suffix '-y' to the noun 'film' (Old English/Old Norse roots 'film'/'filmr'), producing the modern English adjective 'filmy'.

Initially it meant 'having a film or thin membrane'; over time this central idea remained but extended from literal thin membranes to surfaces that appear clouded or to delicate, translucent materials.