Elizabeth?

Wikipedia: Agnes of Austria (1322–1392). The marriage [of Bolko II and Agnes] apparently was childless, although some sources[3] stated that they had two children: a daughter, Elisabeth (d. 1407) and a son, Bolko, who, according to old Silesian legend, died with only nine-years-old, accidentally killed by the court jester Jakob Thau, when he threw a stone to him during a game.