ETYM So called from the fallow, or somewhat yellow, color of naked ground; or perh. akin to Eng. felly, cf. Mid. High Germ. valgen to plow up, Old High Germ. felga felly, harrow.
Cultivated land that is not seeded for one or more growing seasons.
Land plowed and tilled, but left unsown for a season to allow it to recuperate. In Europe, it is associated with the medieval three-field system. It is used in some modern crop rotations and in countries that do not have access to fertilizers to maintain soil fertility.

ETYM AS. fealu, fealo, pale yellow or red.
1. Left unplowed and unseeded during a growing season.
2. Undeveloped but potentially useful.

To plow, harrow, and break up (land) without seeding to destroy weeds and conserve soil moisture.