variety of cabbage in which the young inflorescence forms a fleshy white head, 1590s, originally cole florye, from Italian cavoli fiori "flowered cabbage," plural of cavolo "cabbage" + fiore "flower" (from Latin flora, from PIE root *bhel- (3) "to thrive, bloom").
First element is from Latin caulis "cabbage" (originally "stem, stalk;" see cole (n.1) ) which was borrowed into Germanic and is the source of the cole in cole-slaw and of Scottish kale. The front end of the word was re-Latinized from 18c.; the back end was influenced by flower (n.). The boxer's cauliflower ear, swollen and deformed by blunt trauma, is from 1907.