re: Poker & Folding rather than Checking
I was going to edit the post above, but too much time has passed.
I decided to go and look at the old book we used when I was a kid. Growing up, my grandmother had a book called Official Rules of Card Games
that was used to settle any questions about rules. It was published back in 1968 (claims first edition was 1887) by the United States Playing Card Company. They have a fairly complete list of the "Laws of Poker."
Sure enough, they did address this question:
9.(f): No player may check, bet, call, raise, or drop, except in his proper turn. A player may drop even when he has the privilege of checking. [...]
It should be noted that this book refers to folding as "dropping." Also, look at that non-politically correct grammar usage. They use the masculine form for the personal pronoun! These days this would be rewritten with a bunch of "his or her" and "he or she" verbosity.
How much should we trust this book? Probably not much. Let me include the description of Omaha that this book contains.
Omaha--Each player receives two cards down. Five cards are dealt to the center, face down. There is a betting interval. Then the center cards are turned up one by one. There is a betting interval after each. Each player makes his hand from his own two cards and the five in the center.
Also, this isn't just a messed up Texas
Hold'em variation. They include a Hold'em, which is identical to the one we play today. I have seen other references to an Omaha like the one above. So, maybe that's part of the history. Still weird.