recalcitrant: [19] People who are recalcitrant are etymologically ‘kicking back’ against whatever restrains or upsets them. The word was borrowed from French récalcitrant, a descendant of the present participle of Latin recalcitrāre ‘kick back’. This was a compound verb formed from the prefix re- ‘back, again’ and calcitrāre ‘kick’, which in turn was derived from Latin calx ‘heel’. [recalcitrant etymology, recalcitrant origin, 英语词源]