What does Boxing Day have to do with boxing?
early 13c., flur "flower" (see flower (n.)); meaning "finer portion of ground grain" is mid-13c., from the notion of flour as the "finest part" of meal (cf. French fleur de farine), as distinguished from the coarser parts (meal). Spelled flower until flour became the accepted form c.1830 to end confusion.
"to sprinkle with flour," 1650s, from flour (n.). Related: Floured; flouring.
Grain reduced to the form of meal is spoken of in the time of Abraham (Gen. 18:6). As baking was a daily necessity, grain was also ground daily at the mills (Jer. 25:10). The flour mingled with water was kneaded in kneading-troughs, and sometimes leaven (Ex. 12:34) was added and sometimes omitted (Gen. 19:3). The dough was then formed into thin cakes nine or ten inches in diameter and baked in the oven. Fine flour was offered by the poor as a sin-offering (Lev. 5:11-13), and also in connection with other sacrifices (Num. 15:3-12; 28:7-29).