Leather

Leather is an animal skin used to make armor and books.

Drops from animals hindly quarters (butts)
Cows, mooshrooms, horses, donkeys, mules and llamas drop 0-2 pieces of leather upon death. The maximum amount is increased by 1 per level of Looting, for a maximum of 0-5 leather with Looting III.

Foxes that are holding leather also have a chance of 8.5%‌/100%‌ to drop the leather they are holding upon death. Alternatively, a player can drop a food item, causing the fox to drop the leather.

Fishing
Leather can be obtained as a "junk" item from fishing.

Trading
Leatherworker villagers offer to sell 9–12 leather for one emerald.

Novice-level leatherworker villagers have a $2/3$ chance to buy 6 leather for one emerald in Java Edition, and always offer the trade in Bedrock Edition.

Repairing
Leather armor can be repaired with leather in an anvil.

Issues
Kůže Leder Cuero Cuir Bőr Cuoio 革 가죽 Leer Skóra Couro Кожа 皮革