This is one of those pieces of trivia I've dragged up on occasion that I suspect most people I've told it to speculated I was making up. At long last I present a source.
For many centuries, and perhaps back to Homer, Western society slept in two shifts. People went to sleep, got up in the middle of the night for an hour or so, and then went to sleep again. Thus night — divided into a “first sleep” and “second sleep” — also included a curious intermission.Link




