I believe it's a word used among Assembly of God preachers, as a tribute to some early founder of the church who accidently came to church drunk one sunday and was trying to say "Brain", right? Am I right? What do I win?
Nope, I am not AOG.
A Berean was a group of people in th NT who were commended by Paul for wanting to "prove all things" rather than taking the word of one person over another, even if that person was Paul.
Berean is spelled differently in older NT translations.