Fallow means left unplanted for a season so the soil can rest. Lie fallow, a fallow field, leave the ground fallow.
Medieval farming turned on it: a third of the land lay fallow each year to recover nitrogen, until clover and crop rotation made that waste unnecessary. Figuratively a fallow period is a stretch of no output, and it implies recovery rather than failure.
1adjectivefallowLeft unplanted for a season so the soil can rest.
“The farmer left the field fallow for a year to let the soil recover.”
fallow is a state of land.
Old English fealh meant ploughed land. The colour word fallow, a pale brown, is a different and older word.
Proto-Indo-European
*polḱéh₂ — arable land
Proto-West Germanic
*falgu
Old English
fealh
Middle English
falwe
English, today
fallow
Built from
From Middle English falwe, from Old English fealh, fealg (“fallow land”), from Proto-West Germanic falgu (compare stq Falge, West Frisian falig, felling, Dutch valg, German Felge), from Proto-Indo-European polḱéh₂ (“arable land”) (compare cel-gau olca, Russian полоса́).
Etymology from Wiktionary, CC BY-SA