Icy Scale Leggings

Icy Scale Leggings are mail leg armor that give a bonus to Agility, Stamina, and Frost Resistance. These were added in Patch 1.11 to help players with the frost damage-oriented Naxxramas.

Source
Icebane Leggings are quest reward from if they have completed the quest Echoes of War. Wilhelm will make you this item if you supply him the components.

The components are:
 * 2 Frozen Rune
 * 2 Blue Sapphire
 * 2 Essence of Water