fallow (n.) Look up fallow at Dictionary.com
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 in English to fallow (adj.) 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.) Look up fallow at Dictionary.com
"pale yellow, brownish yellow," Old English fealu "reddish yellow, yellowish-brown, tawny, dusk-colored," 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, 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).