What exactly is "noise"?

[x-class]

For an example: Lets say that it says, Siberian 1% . Then someone would say its just "noise". Here is another example Ashkenazi 0,0 - 0,3% , then someone would say its just "noise". What does "noise" mean? Does it mean that it's an error or does it mean that there is some of that ancestry but very far far back?

[Hayalet]

irrelevant or meaningless data or output occurring along with desired information