What is the origin of the idiom "wild card" and when to use it?

The idiom "wild card" originated from card games, particularly poker, where certain cards were designated as "wild," meaning they could represent any other card. Over time, the phrase has been adopted into various contexts, referring to an element or factor that introduces unpredictability or a level of uncertainty into a situation. In general usage, this expression is used to refer to something or someone that is unexpected, unconventional, or has the potential to alter the usual course of events.