When do you use this expression?
Native speaker’s answer
Rebecca
I do not recommend using this expression as an English learner. This expression could very easily be taken as offensive without the person saying it knowing the exact person and situation to use it, since this expression is usually a diss. "Big fella" means "big guy", and "big" could refer to either the other person's status or physical appearance. It is said to address someone in a disrespectful way, either jokingly or seriously.