Polar Tunic

Polar Tunic is a Leatherworking-made leather chest piece that gives a bonus to stamina, agility and frost resistance. The recipe to make this can no longer be learned. The Frozen Rune material component is also no longer available.

Source
This item was crafted by Leatherworkers with a skill level of 300. Non-crafters could also get this item from if they completed the quest. Wilhelm could make you this item if you supply him the components and.

The components were:
 * 7 Frozen Rune
 * 16 Enchanted Leather
 * 4 Cured Rugged Hide
 * 2 Essence of Water
 * 4 Ironweb Spider Silk

The pattern was learned from a quest you got from Master Craftsman Omarion, who was located in the Deathknights wing of the original Naxxramas. The quest required you to return Omarion's Handbook to Light's Hope Chapel and give it to Craftsman Wilhelm. He would then instruct you if you were a craftsman. You also had to be Exalted with the Argent Dawn to learn this pattern.