button: [14] Button comes via Old French bouton from Vulgar Latin *botōne, a word connected with the verb *hottāre ‘thrust’ (from which ultimately English gets butt ‘hit with the head’). The underlying notion contained in button is thus of something which pushes up, thrusts itself outwards, rather like a bud growing on a plant; the fact that the resulting round knob is used for fastening is, from the point of view of the word’s semantic history, secondary. (Inconclusive attempts have in fact been made to link bud with Old French boter, a descendant of Vulgar Latin *bottāre, and from the 15th century the word button has been applied in English to ‘buds’.) => butt
