Here's a breakdown:
* "In" is a prefix meaning "not" or "the opposite of."
* "Cred" comes from the Latin word "credere," meaning "to believe."
Therefore, "incredulous" means "not believing" or "unwilling to believe."
It's important to note that this combination is not always used together. "In" can be combined with other word parts to create different words with different meanings, and "cred" is often used in other words related to belief, such as "credence" and "credit."