This term derives from what was once pronounced as "Yeah Yeah", but slowly over time has accelerated into the condensed version as one big word "eyaeya" and can be used in any scenario, and is commonly used as a greeting. It can also be used as an expression affirming or verifying a statement or question.
Person ONE: "Eyaeya what's up?"
Person TWO: "Eyaeya not much."
Person ONE: "You going to the game later?"
Person TWO: "Eyaeya"