fal·low¹ / ˈfalō/ • adj. (of farmland) plowed and harrowed but left unsown for a period in order to restore its fertility as part of a crop rotation or to avoid surplus production: incentives for farmers to let the land lie fallow in order to reduce grain surpluses. ∎ fig. inactive: long fallow periods. ∎  (of a sow) not pregnant.• n. a piece of fallow or uncultivated land.• v. [tr.] leave (land) fallow.DERIVATIVES: fal·low·ness n.fal·low² • n. a pale brown or reddish yellow color.

fallow2 reddish-yellow (now only in fallow deer). OE. f(e)alu, obl. fealwe, etc. = OS. falu (Du. vaal), OHG. falo (G. fahl, falb), ON. fǫlr :- Gmc. *falwaz, f. IE. *pol- *pel- *pl-, as repr. by Skr. palitás grey, Gr; poliós, pelitnós grey, pellós dark-coloured, L. pallēre be pale, pullus grey, blackish, (O)Ir., Gael. liath, W. llwyd grey, OSl. plavŭ white.

fallow1 ploughed or arable land OE.; ground ploughed and harrowed but left uncropped XVI. OE. fealh, fealg- = MLG. valge (G. felge); used as adj. XIV.
Hence fallow vb. break up (land) as for sowing. OE. fealgian = MHG. valgen, velgen.