The English word firebrand was more than likely established in the late 13th century in England. Its' figurative meaning of "someone that kindles mischief or passions" is from the late 14th century...
I found this on the Internet firebrand \FYRE-brand\ noun 1 : a piece of burning wood *2 : one that creates unrest or strife (as in aggressively promoting a cause) : agitator Example sentence: John...