Poker is a development of il frusso (played in Italy in the 15th century). In a Canzone of Lorenzo de Medici, Flush (il Frusso) and Bassett are referred to.
A similar but less game, called primiera, was also played in Italy in the 16th century, whence under the name of primero it traveled to Spain. La prime is mentioned by Rabelais (16th century); and later the game of prime elaborated was played in France under the name of l’ambigu or le mesle.
Prime was also played in England in the 16th century; and later a bastard kind of prime, called post and pair, was much played in the west of England.
Gleek has some points of resemblance to these games, The more modern game of brag is only post and pair with variations.
Poker (originally played in America) may be described as developed brag, though in some respects it "throws-back" to the parent games post and pair, l’ambigu, and primero.
Encyclopaedia Britannica, 9th Edition (1875) and 10th Edition (1902).
"The American Hoyle: or, Gentleman's hand-book of games" by William Brisbane Dick, 1895
The Card Players by Theodoor Rombouts (1597–1637)