We have a lot of credence when it comes to English, as we put a lot of our trust into the language. It truly is incredible just how expansive its roots go, so much so that you have to give credit to those who helped create it: the Romans. Many of our words that have to do with trust and belief come from the Latin root credere. Here are a few examples of its uses in everyday language:
Accredit- To attribute to (ac- = to, -credere- = trust)
Creditable- Praiseworthy (-credere- = trust, –able = able to)
Credulous- Gullible (-credere- = believe, –ulous = habitual)
Credentials- Qualification (-credence- = acceptance, -al = relating to)
Incredible- Unbelievable (in- = not, -credere- = believe, -ible = able to)
For further reading: Dictionary of Greek and Latin Origins by Bob Moore (1997)