flour: [13] Etymologically, flour is the same word as flower. It originally meant the ‘flower’, or ‘finest part’, of ground grain, and hence eventually just ‘ground (and more or less sifted) grain’. The distinction in spelling between flour and flower did not emerge until the late 18th century, and the spelling flower for ‘flour’ persisted into the early 19th century. => flower
flour (n.)
"finer portion of ground grain," mid-13c., from flower (n.), and maintaining its older spelling, on the notion of flour as the "finest part" of meal, perhaps as the flower is the finest part of the plant or the fairest plant of the field (compare French fleur de farine), as distinguished from the coarser parts (meal (n.2)). Old French flor also meant both "a flower, blossom" and "meal, fine flour." The English word also was spelled flower until flour became the accepted form c. 1830 to end confusion. Flour-knave "miller's helper" is from c. 1300.
flour (v.)
"to sprinkle with flour," 1650s, from flour (n.). Meaning "convert (wheat) into flour" is from 1828. Related: Floured; flouring.