How to get the mending enchantment?

I have a skeleton farm and I enchanted DOZENS of items already. I never saw "mending" though. The Wiki says, that you find this on the lower enchanting levels, but I never saw it.

Note: (Normally) Before I enchant an item, I look through all of them and check on each what I would get: Helmet, Chestplate, Leggings, Boots, Sword, Bow. I think chances that I really never could have seen it are pretty low.

Can you get this enchantment only from the end and from books? I saw some enchanted items in the end cities with mending.

Mending is a treasure enchantment, which you can only find in the world, you can not create it yourself on an enchanting table.

Treasure enchantments can be obtained by

• Fishing
• Chests in dungeons, temples, mineshafts, End cities etc.
• Trading (villagers charge double price for treasure enchantments)

Mending can be found on many items, including, for example, Fishing Rods.

Sources: 1.9 changelog, enchantment mechanics, trading pages.