This phrase is believed to be derived from the old words will-ye. nill-ye (or will-he, nill-he) meaning whether you want to or not (or whether he wants to or not).
TONGUE IN CHEEK
In the 18th century sticking your tongue in your cheek was a sign of contempt. It is not clear how speaking with your tongue in your cheek took on this modest meaning.
THROW DOWN THE GAUNTLET
In the Middle Ages a gauntlet was the glove in a suit of armour. Throwing down your gauntlet was a way of challenging someone to a duel.
FEET OF CLAY
If a person we admire has a fatal weakness we say they have feet of clay. This phrase comes from the Bible. King Nebuchadnezzar dreamed of a statue. It had a head of gold, arms and chest of silver, belly and thighs of bronze and its legs were of iron. However its feet were made of a mixture of iron and clay. A rock hit the statue's feet and the whole statue was broken. The prophet Daniel interpreted the dream to be about a series of empires, all of which would eventually be destroyed. (Daniel 2:27-44)