News to me, via Lapham’s Quarterly: In 1969 Vladamir Nabokov was interviewed for an article in The New York Times, and was asked, “How  do you rank yourself among writers (living) and of the immediate past?” His response:

I often think there should exist a  special  typographical sign  for  a  smile–some sort of concave mark, a supine round bracket, which I would now like  to  trace  in  reply  to  your question.

Nabokov’s typographical concept would become a reality in 1982 when Scott E. Fahlman, a computer scientist at Carnegie Mellon University posted the following message on a university bulletin board:

I propose that the following character sequence for joke markers:

: -)

Read it sideways. Actually, it is probably more economical to mark things that are NOT jokes, given current trends. For this, use : -(