Here's a breakdown:
* Leather is known for its strength and resilience. It's used for making things like shoes, belts, and jackets that need to withstand a lot of use.
* Tough refers to being hard to break, damage, or wear down.
Therefore, comparing something to leather implies that it possesses these qualities of strength and durability.
Examples:
* "The old man's hands were as tough as leather from years of hard work."
* "The new tires are as tough as leather, they can handle any terrain."
* "The company's reputation is as tough as leather, they've faced many challenges and come out stronger."