flower

The Latin word flos (genitive floris) meant the blossom of a plant, but Romans extended it to mean the finest, choicest part of anything. Flos farinae was the flower of flour: the lightest sifted powder from milled grain. Both senses traveled together into Old French as flor and flour, and from there into Middle English, where one spelling covered both the plant bloom and the powdery kitchen staple well into the 1700s.

Latin flos itself descends from the Proto-Indo-European root bhleh₃-, meaning to bloom or to swell. That root produced a wide family: the Latin florere (to flourish), floridus (blooming, ornate), Flora (goddess of spring flowers), and eventually the English words flourish and florid. The root reached Latin through an Italic ancestor and left no surviving trace in the Celtic or Germanic branches, which means English borrowed it entirely from French rather than inheriting it from Old Germanic.

In Middle English, flour or flower arrived via Anglo-Norman after 1066. Geoffrey Chaucer used flour in the late 14th century for both plant blossoms and milled grain. The two meanings coexisted without confusion for centuries because context made the sense plain. By about 1350, the plant meaning began to attract the spelling flower, while the milled grain meaning kept flour: a typographical divergence that took another three centuries to fully settle.

The spelling flower stabilized for the botanical sense in the 17th century, while flour remained for the milled product, completing one of English's tidiest semantic splits. Both are legitimate descendants of the same Latin root. Both preserve one of Rome's own metaphors: that the finest part of anything is its flower, and that what is finest deserves its own name.