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Wiktionary
fonio

n. 1 ''Digitaria exilis'', a (l en cereal) (l en cultivate cultivated) in western (l en Africa) 2 ''Digitaria iburua'', a (l en cereal) (l en cultivate cultivated) in western (l en Africa)

Wikipedia
Fonio

Fonio is the term for two cultivated grains in the Digitaria genus which are notable crops in parts of West Africa. The grains are very small. The crops have C metabolisms and are medium in height. The number of chromosomes for the species can be diploid (2n), tetraploid (4n), or hexaploid (6n).

The name (borrowed by English from French) is from Woloffoño.