Thanks! I will add to my list of cryptic threats.This is how I've always understood it.
Hilary: "'Bow up' can also describe a person who is about to fight someone else. Example: He got the red ass and was all bowed up to punch that guy." Emily: "It comes from the idea of getting ready to fight, where a guy throws back his shoulders and his chest bows outward. So 'bow up' is equivalent to 'start a fight.