fallowyoudaoicibaDictYouDict[fallow 词源字典]
fallow: English has two words fallow, both of considerable antiquity. Fallow ‘uncultivated’ [OE] originally meant ‘ploughed land’. Its present-day adjectival meaning ‘ploughed but not sown’ or, more broadly, just ‘uncultivated’, developed in the 15th century. Fallow ‘pale yellowish-brown’ [OE] (now used only in fallow deer) comes via Germanic *falwaz from Indo- European *polwos, a derivative of the base *pol-, *pel-, which also produced English appal [14] (originally ‘grow pale’), pale, and pallid.

Its Germanic relatives include German fahl ‘pale, fawn’ and falb ‘pale yellow’. (Germanic *falwaz, incidentally, was the ancestor of French fauve ‘wild animal’, source of the term fauvism [20] applied to an early 20th-century European art movement that favoured simplified forms and bold colours.)
=> appal, pale, pallid[fallow etymology, fallow origin, 英语词源]
fallow (n.)youdaoicibaDictYouDict
c. 1300, from Old English fealh "fallow land," from Proto-Germanic *falgo (cognates: Old High German felga "harrow," German Felge "plowed-up fallow land," East Frisian falge "fallow," falgen "to break up ground"), perhaps from a derivation of PIE root *pel- (3) "to turn, fold." Assimilated since Old English to fallow (adj.), according to OED probably because of the color of plowed earth. Originally "plowed land," then "land plowed but not planted" (1520s). As an adjective, from late 14c.
fallow (adj.)youdaoicibaDictYouDict
"pale yellow, brownish yellow," Old English fealu "reddish yellow, yellowish-brown, tawny, dusk-colored" (of flame, birds' feet, a horse, withered grass or leaves, waters, roads), from Proto-Germanic *falwa- (cognates: Old Saxon falu, Old Norse fölr, Middle Dutch valu, Dutch vaal, Old High German falo, German falb), from PIE *pal-wo- "dark-colored, gray" (cognates: Old Church Slavonic plavu, Lithuanian palvas "sallow;" Greek polios "gray" (of hair, wolves, waves), Sanskrit palitah, Welsh llwyd "gray;" Latin pallere "to be pale"), suffixed form of root *pel- (2) "pale" (see pallor). It also forms the root of words for "pigeon" in Greek (peleia), Latin (palumbes), and Old Prussian (poalis). Related: Fallow-deer.