filmyoudaoicibaDictYouDict[film 词源字典]
film: [OE] The notion underlying film is of a thin ‘skin’. The word comes ultimately from a prehistoric Germanic *fellam, which was related to Latin pellis ‘skin’ (source of English pelt ‘skin’). From this was derived *filminjam, which produced Old English filmen, a word used for various sorts of anatomical membrane or thin skin, including the peritoneum and the foreskin of the penis.

It was generalized from the late 16th century to any thin membrane, and was applied by early 19th-century photographers to a thin layer of gel spread on photographic plates (‘The film of isinglass … peels off and will be found to bear a minute copy of the original’, William Thornthwaite, Guide to Photography 1845). As photographic technique moved on to cellulose coated with photosensitive emulsion, it took the term film with it.
=> pelt[film etymology, film origin, 英语词源]