The character 'fly (飛)' from Hihaku meant active movement of the brush, and the character 'white (白)' meant the faded line of the Kanji characters; Hihaku was named by Sai Yo of the Later Han Dynasty, who came up with the idea when he saw a person writing letters with a large brush.
飛白の「飛」は筆勢の飛動を、「白」は点画のかすれを意味し、後漢の蔡ヨウが、人が刷毛で字を書いているのを見て考え出したという。