furyoudaoicibaDictYouDict[fur 词源字典]
fur: [14] Old English did not have a distinct word for ‘animal’s hair’ – the nearest approach to it was fell ‘animal’s hide’. Then in the 13th century English acquired the verb fur ‘line with fur’ from Anglo-Norman *furrer or Old French forrer ‘encase, line’. These were derivatives of the Old French noun forre ‘sheath, case’, a loanword from prehistoric Germanic *fōthram ‘sheath’, which in turn goes back to the Indo-European base *pō- ‘protect’.

In the 14th century the new English verb was taken as the basis for a noun, which originally meant ‘trimming for a garment, made from fur’, or more loosely ‘garment made from fur’; it was not until the 15th century that it was used for ‘animal’s hair’.
[fur etymology, fur origin, 英语词源]
fur (n.)youdaoicibaDictYouDict
late 14c. "trimming or lining of a garment" (implied c. 1300 in surname Furhode "fur hood"), probably from Old French forrer, fourrer "cover with fur, line (clothing)," in general "to cover, fill with," from fuerre "sheath, scabbard" (via notion of "covering"), from Frankish *fodr or another Germanic source, from Proto-Germanic *fodram "sheath" (cognates: Old Frisian foder "coat lining," Old High German fotar "a lining," German Futter, Gothic fodr "sword sheath"), from PIE root *pa- "to protect, feed" (see food (n.)).

First applied c. 1400 to the hairy pelt of an animal, whether still on the animal or not. The Old French noun might have had the sense "hide, fur, pelt" (and thus might serve as the immediate source of the English noun), but this is not attested. Absent this, the sense transfer from the lining to the material that goes to make it probably happened in English. As an adjective from 1590s.
I'le make the fur Flie 'bout the eares of the old Cur. [Butler, "Hudibras," 1663]
fur (v.)youdaoicibaDictYouDict
c. 1300 (implied in furred), from fur (n.) or Old French fourrer "to line." Related: Furring.