Meaning

noun a member of the genus Fagopyrum; annual Asian plant with clusters of small pinkish white flowers and small edible triangular seeds which are used whole or ground into flour

noun grain ground into flour

originUltimately from Middle Low German bōkwête (“beech-wheat”) (so called because of its triangular seeds, which resemble the much larger seeds of the beech nut from the beech tree, and the fact that it is used like wheat), probably via Middle Dutch boecweit, boecweite. Compare German Buchweizen. Despite the name, buckwheat is not related to wheat, as it is not a grass.

Etymology from Wiktionary, CC BY-SA 3.0