Derring-do is the quality of being bold, often in a rather showy or foolish way. deeds/acts etc of derring-do very brave actions like the ones that happen in adventure stories - used humorously (dorring don (14-15 centuries))
He left Terminus in a sullen distemper. No one was at the port to see him off. He, Homir Munn, was risking his neck in derring-doery of the most outrageous sort, and yet he left alone.