Passage: Three years later in 1159, Yoshitomo and Fujiwara no Nobuyori placed Go-Shirakawa under house arrest and killed his retainer, the scholar Fujiwara no Michinori, in what is called the Heiji Rebellion.  Eventually, Taira no Kiyomori, in support of Go-Shirakawa, defeated Yoshitomo.While escaping from Kyoto, Yoshitomo was forced to kill his son Tomonaga.  Later, Yoshitomo was betrayed and killed in his bath. Three of his sons, Yoritomo, Minamoto no Yoshitsune and Minamoto no Noriyori, were later spared and exiled by Kiyomori.  However, Yoshihira and Nobuyori were executed.His grave in Aichi Prefecture is surrounded on all sides by wooden swords (bokuto), as by legend his last words were "If only I had even a bokuto..."

Question: What does bokuto stand for?
wooden swords