It has also been inferred that the character '清' representing the "kiyo" in TAIRA no "Kiyomori" as well as in "Yoshikiyo" comes from the fact that Yoshikiyo was eboshioya (the person who wears an eboshi [black-lacquered headgear, which is made of silk, cloth or paper, originally worn by court nobles in ancient Japan, and afterwards spreading to the common people] at Kiyomori's coming of age ceremony).
また、平清盛の「清」の一字は、彼が烏帽子親となったことに由来するともいう。