Nibiru, to the Babylonians, was the celestial body associated with the god Marduk. The name is Akkadian and means 'crossing place' or 'place of transition'. In most Babylonian texts it is identified with the planet Jupiter. In Tablet 5 of the Enuma Elish it may be the pole star, which at the time was Thuban or possibly Kochab (Ursa Minor).
The term "Nibiru" comes from the Sumerian cuneiform tablets and writings dating 5,000 years old. The term Nibiru means "Planet of the crossing", and it's cuneiform sign was often a cross, or various winged disc. The Sumerian culture was located in the fertile lands between the Euphrates and Tigris rivers, at the southern part of today's Iraq.
Due to its use in opposition to the phrase itebbiru "who used to cross," Landsberger and Kinnier Wilson suggest that it refers to a stationary point in the heavens.1 In a reconstruction of Tablet V of the Enûma Elish by Landsberger and Kinnier Wilson, the word ni-bi-ri (variant: ni-bi-ru and ni-bi-a-na) is translated as "pole star."1 The authors add in the footnotes that "Applied to Marduk, there is no question that in the late periods neberu is a planet, whether Jupiter or Mercury" however for the referenced translation of Tablet V, "pole star" is used.