Sūn Wù kōng
· Monkey King
· Sun Wukong (name of a monkey with supernatural powers in the novel Journey to the West 西遊記 | 西游记)
· surname Sun
==> Family name of Sun because in the past people called monkeys as Sun.
==> Here it means he knows emptiness.
· free time
· in vain
==> Studying the Buddhist teachings, he has reached some understanding of 'Emptiness'.