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]
film (n.)youdaoicibaDictYouDict
Old English filmen "membrane, thin skin, foreskin," from West Germanic *filminjan (cognates: Old Frisian filmene "skin," Old English fell "hide"), extended from Proto-Germanic *fello(m) "animal hide," from PIE *pel- (4) "skin, hide" (cognates: Greek pella, Latin pellis "skin").

Sense of "a thin coat of something" is 1570s, extended by 1845 to the coating of chemical gel on photographic plates. By 1895 this also meant the coating plus the paper or celluloid. Hence "a motion picture" (1905); sense of "film-making as a craft or art" is from 1920.
film (v.)youdaoicibaDictYouDict
c. 1600, "to cover with a film or thin skin," from film (v.). Intransitive sense is from 1844. Meaning "to make a movie of" is from 1899. Related: Filmed; filming.