I read Ничего at first as nothing, and thought it was a double negative, as in saying, there is nothing he doesn't know. I was apparently wrong.
Jon Snow is a character in "Game of Thrones"
John Snow was a 19th century English physician who pioneered the use of anesthesia and hygiene in surgery.
Also, though I'm sure it's not relevant, John Snow was very coincidentally one of my ancestors from about 300 years ago.