Does Scripture actually call Jesus' disciples " believers?"

I'm currently working on a Bible Study Titled "from believer to follower" Closer to God through his Word. I actually can't find one Instance where us saints/disciples, etc. are called believers! I realize the word is in some translations of the Scriptures, BUT when I look up the original word, it's actually just "brethren." Seems the translators themselves chose to use the word believer(s). Is there anywhere in Scripture where the original form and language refers to us as believers? Thanks for any help you can provide!