From the Glossary of the Wheel of Time:

The people of the Aiel Waste. Fierce and hardy. Also referred to as Aielmen. They veil their faces before they kill, giving rise to the saying "acting like a black-veiled Aiel" to describe someone who is being violent. Deadly warriors with weapons or with nothing by their bare hands, they will not touch a sword. Their pipers play them into battle with the music of dances, and Aielmen call battle "the Dance" or "dancing the spears."