The term "waterproof" is used interchangeably with "water-resistant" and means that moisture can be kept from penetrating. However, the terms "waterproof" or "water-resistant" never guarantee complete protection against
This distinguishes the term from "waterproof," which means that under specified conditions, no water can penetrate. For example, a waterproof storage box can keep the items inside dry even if the box is completely submerged in water. A water-resistant box, on the other hand, would only be able to keep out a certain amount of water and splashes.
To make leather bags waterproof, the material can be waterproofed. You can find more on this topic under the keyword “waterproofing.”
Source: https://ousuca.com/wasserdicht-wasserfest-unterschied/, as of May 31, 2018
