To throw down the gauntlet, to offer or send a challenge. The gauntlet or glove was thrown down by the knight challenging, and was taken up by the one who accepted the challenge.

Note: The gauntlet of the Middle Ages was sometimes of chain mail, sometimes of leather partly covered with plates, scales, etc., of metal sewed to it, and, in the 14th century, became a glove of small steel plates, carefully articulated and covering the whole hand except the palm and the inside of the fingers.

{1913 Webster}