Re: Decimate. This is from the Roman army, where punishment for insubordination within a century (a group of about 80 men, originally 100 but never at full complement in reality) was that the soldiers themselves had to kill one tenth of their own number, the victims being chosen at random by the centurion, IIRC. So while it's true that the end result was only the loss of one tenth of the troops, its effect was more dreadful and more dreaded than the numbers might imply.