1. Greek: "Illiana" could be a variant of the Greek name "Eliana", which itself is a variant of "Eliana", meaning "Jehovah has answered" or "God has answered".
2. Slavic: It could also be a variation of the Slavic name "Ilyana", which is a derivative of "Ilya" meaning "God is my God".
3. American: The name "Illiana" is also sometimes used as a name for the state of Illinois, which itself is a Native American word meaning "tribe of the strong men".
Therefore, the origin of the name "Illiana" is likely a combination of these influences, and its specific meaning may vary depending on its usage.
It's worth noting that the name "Illiana" is not as common as its potential origins, so it's difficult to definitively pinpoint a single origin for the name.