Long ago, all the great tribes of the giants came together for the trial of one particularly heinous criminal. Even among giants, he was phenomenally wicked. Most called for for his immediate execution, but cooler heads prevailed and it was agreed he would be judged by a jury of his peers. So, the long process of choosing jurors began, and finally, one by one, they were selected.
On the day of the trial, the jurors filed into the great cavernous courtroom. Frost giants, cloud giants, storm giants all took their seats. However, one seat remained empty. The accused giant's defense attorney immediately called for a mistrial, because the rules of the court were clearly not being observed. "A jury of twelve!" He thundered. "My client must be judged by a jury of twelve of his peers!" He folded his arms, confident that his client would now go free.
The prosecuting attorney stood and adjusted his dragonhide tie. "Your honor, how many jurors do you see?"
The judge, a venerable old Stone Giant known for his impartiality and fairness, looked and said, "Sir, I see only eleven there."
"You are in error, Your Honor." He dramatically pointed to an ettin, who by chance had been the last to enter and take his seat. "How many are there sitting in judgement? Twelve, if you count the last one twice."
Whew.