To Throw Down The Gauntlet
This phrase means to issue some form of a challenge. The gauntlet (or le gantelet) was a glove composed of jointed steel plates that were worn by knights in armour who used to throw it down to anyone who had offended them, as a sign that they were to fight till one was slain, or confessed himself to be vanquished. In years to come, it became the custom for an ordinary glove to be thrown down instead. If the challenge was then accepted, the person to whom the glove was thrown picked it up.
Words by Adam Jacot de Boinod, author of The Meaning of Tingo and Other Extraordinary Words from around the World, published by Penguin Books and creator of the iPhone App Tingo, a quiz on Interesting Words