Why is begonia flower called Jieyu flower? Any allusions?

Begonia flower is called Jieyu flower. Source: Five Dynasties Wang Renyu's Explanation of Kaiyuan Tianbao's Legacy

Begonia flower (scientific name: begonia? (Ait。 ) Borkh): trees, up to 8 meters; Branchlets stout, cylindrical, pubescent when young, gradually falling off, reddish brown or purplish brown when old, glabrous. The leaves are ovoid to oblong, 5-8 cm long and 2-3 cm wide, and the edges are closely serrated, sometimes close to the whole. When young, the upper and lower surfaces are sparsely pubescent, then fall off, and the old leaves are hairless. Inflorescence is nearly umbrella-shaped, with 4-6 flowers, 4-5cm in diameter, 2-2.5cm in length and1.5-2cm in width, with short claws at the base and white and pink buds. The fruit is nearly spherical, 2 cm in diameter and yellow. Result period: August-September.

Begonia flower is a tree, which can reach 8 meters high; Branchlets stout, cylindrical, pubescent when young, gradually falling off, reddish brown or purplish brown when old, glabrous; Winter buds are ovate, the apex is acuminate, puberulent, purple-brown, with several exposed scales. Leaf blade elliptic to oblong, 5-8 cm long and 2-3 cm wide, with short conical or obtuse tip, wide wedge-shaped or nearly round base and densely serrated edge.

As early as the pre-Qin period, the history of begonia flower cultivation was recorded in ancient China. By the Han Dynasty, Begonia flowers had formed an indissoluble bond with garden art, and by the Tang Dynasty, both cultivation techniques and planting area had been significantly improved. In the Song Dynasty, the Begonia flower got greater development on the basis of the Tang Dynasty, and finally reached its peak. At that time, it was regarded as "the statue of a hundred flowers".