Just a few minutes ago hail was hurtling down out of the sky and bouncing all over the place. I heard it first, and then when I looked out the window, I heard my grandmother's voice in my head, saying "Look at that! It's hailing fit to beat the band!"-- at the moment I realized it was hail, not rain pummeling every surface in sight. And then it occurred to me that although I know what the expression "fit to beat the band" means, I don't have a clue where it came from. It's just one of those mysterious idioms people use. Other expressions from that generation my grandparents frequently used was "a hill of beans, "living daylights," and "all the tea in China." (I'm sure more will come to me, if I think longer about it.) A lot of these expressions are still with us, since certain idioms and piece of slang continue to appeal to succeeding generations. (Like "cool," for instance.)
Which then led me to think about the inverse, and how irritated I felt just a few days ago, reading a scene in a novel (published in 2010) depicting someone using the expression "Duh" (in its current, not its former, sense) in 1973. I can assure you, no one said "duh" in 1973. The author probably had not yet been born in 1973. And I could easily believe the book's editors hadn't been, either. Come to think of it, "Life on Mars" (both the British and the US series) were loaded with similar kinds of anachronisms. (But of course the makers of both of those shows could cover themselves by noting that they weren't depicting life in 1973 New York or London, only dreams or fantasies about it, and even claim, if they wanted to, that anachronisms were deliberate.)
Yikes! I'm supposed to be working, not daydreaming about the mysteries of slang.