Poker Face is a term that was derived from poker as there is a deliberate attempt from players to hide their emotions at the table irrespective of the cards held.
The “poker face” is achieved by appearing blank or having a neutral facial expression to prevent giving away any information.
EXAMPLE: “Not a very good poker face when I’ve tried bluffing at the casino, most of the time I will be called.”
If you have watched high stakes professionals like Phil Ivey play live, their poker faces would be expressionless. This is because they do not want their opponents to know the strength of their hands.