I was reading The Iliad and there's this word in it: greaves. What's that?

armor for the leg.

First [Alexandrus] greaved his legs with greaves of good make and fitted with ankle-clasps of silver; after this he donned the cuirass of his brother Lycaon, and fitted it to his own body; he hung his silver-studded sword of bronze about his shoulders, and then his mighty shield.

From Homer's The Iliad.