"Bust a cap" is the current bastardization of a 19th century hrase in which a person would 'bust a cap', that is to say, bust the cap of their flint lock weapon.
Croatian meaning only
cap 'tzap' - multifunctional word used in all imaginable situations to express agreement, excitement, satisfaction of oneself or surprise. Invented & first used by former Croatian rapper, now a mental patient, Target.