card game, 1834, American English, of unknown origin, perhaps from the first element of German Pochspiel, name of a card game similar to poker, from pochen "to brag as a bluff," literally "to knock, rap" (see poke (v.)). A popular alternative theory traces the word to French poque, also said to have been a card game resembling poker. "[B]ut without documentation these explanations are mere speculation" [Barnhart]. The earlier version of the game in English was called brag.
The game itself originated apparently by 1829, according to later reminiscences, in and around the lower Mississippi region, perhaps among riverboat gamblers. The original form seems to have been played with a 20-card pack (A-K-Q-J-10) evenly dealt among four players; the full-deck version was played by the 1840s.
Slang poker face (n.) "deadpan" is from 1874.
A good player is cautious or bold by turns, according to his estimate of the capacities of his adversaries, and to the impression he wants to make on them. 7. It follows that the possession of a good poker face is an advantage. No one who has any pretensions to good play will betray the value of his hand by gesture, change of countenance, or any other symptom. ["Cavendish," "Round Games at Cards," dated 1875]
To any one not very well up in these games, some parts of the book are at first sight rather puzzling. "It follows," we read in one passage, "that the possession of a good poker face" (the italics are the author's) "is an advantage." If this had been said by a Liverpool rough of his wife, the meaning would have been clear to every one. Cavendish, however, does not seem to be writing especially for Lancashire. [review of above, "Saturday Review," Dec. 26, 1874]