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. 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