A variation on "tuber" which is a nodule found on plants that collects nutrients. Therefore, a "boober" is a nodule that collects "boo" or disapproval (as in an audience booing). Therefore, a booberface is someone who has disapproval directed at them, and it implies that this produces (imaginary) nodules on their face filled with that disapproval.
"You are a booberface."
"I have grown a beard to hide the boobers covering my face."
"As the crowd has not enjoyed my performance, I have become a booberface, and now I question my life's validity."