Final answer:
The phrase 'throw down the gauntlet' is an English idiom meaning to issue a challenge. It has historical roots in medieval knighthood and is used today to signify a preparedness for confrontation or debate.
Step-by-step explanation:
The phrase 'throw down the gauntlet' is an idiom in the English language that originates from the practices of medieval knighthood. The phrase signifies a challenge, specifically one that is issued in a dramatic or public manner. The etymology of this phrase comes from the days of chivalric tournaments, where a knight would throw his gauntlet, which is a heavy glove, to the ground as a way of challenging another knight to a duel. The other knight would pick up the gauntlet to accept the challenge. Today, the phrase is used metaphorically to denote throwing down a challenge in general, and it often implies that the challenger is ready and willing to engage in a contest or debate.