Time for a nooner

Whats the history of this expression?

I've never heard this one before, but it sounds to me like it means 'time for a lunch time drink'. Which by-the-way sounds like a superb idea to me and seeing it's 12.40 here in the Blue Mountains, I'm gonna do just that.

You know how people are so busy that they try to get things done on their lunch hour. Well...

NOONER -- noun. 1. 1940s+ a midday alcoholic drink. 2. 1970s+ sexual intercourse, often adulterous, enjoyed around lunchtime (afternoon delight). From Cassell's Dictionary of Slang by Jonathon Green (Wellington House, London, 1998).

I once heard from people in St. Joseph, Missouri that the birth rate was higher in small towns because people go home for lunch. In commuter cities ... well, I guess that's where the "often adulterous" comes in.