The word is Greek and means, "land between the rivers." You are probably confused by what it means because it is often used to designate a country or ethnicity, which it is not. It is an ancient melting pot for many nations and tribes. Mesopotamia includes most of the valley between the Euphrates and the Tigris Rivers. The area has been conquered and re-conquered for ages, including by the "Barbarians" from northern Europe.
Suellen Ocean is the author of Secret Genealogy a how-to for tracing ancient Jewish ancestry available at Amazon and B&N.