You can now search Google's database of books for the relative frequency with which words or terms show up, by year (or decade) of publication. I was curious about whether "poker" would show an increasing trend over time; after all, there were very few poker books written prior to World War II.
I was therefore surprised at the curve generated, showing a peak in the mid-1940s, and a substantial decline since. (There is a little rise just in the last few years before 2000, which might be attributable to the boom in poker and poker publishing, or might just be statistical noise. Too early to tell.)
For comparison, I also checked "blackjack," "roulette," and "gambling." None of them showed the same kind of trend line.
I'm puzzled by this. Maybe a lot of the references are noncontextual, i.e., referring to fireplace pokers rather than to the game. If so, that would help explain why the other words do not follow similar patterns. Or maybe it's a sampling error problem--i.e., a higher fraction of 1940s books that mention poker found their way into Google's database than was the case in the 1980s.
But I really have no solid idea. Theories, readers?