I’ve heard on more than one occasion someone “dad joke” about denial not just being a river in Egypt. Online you’ll find this quote attributed, without further detail, to Mark Twain. However, the earliest evidence of its use, according to Quote Investigator, was in a 1933 U.S. newspaper – 23 years after Twain died. It’s interesting, though not surprising, how the unverified attribution presented as fact is clearly more prevalent on the Internet.