This video shows, the meaning of the Sumerian word from the Oriental Institute.
You can also read Dr Mike Heiser’s debunking of Nibiru at this link.
Heiser did a similar thing as the guy in this video too.
Here is an intro to Heiser’s paper on this matter.
“Is Sitchin correct – Is Nibiru a 12th planet that passes through our solar system every 3600 years? Did the Sumerians know this? Unfortunately for Sitchin and his followers, the answer to each of these questions is no. But how do I know?”