At one time the whole earth had the same language and vocabulary.
References for Genesis 11:1
As people migrated from the east, they found a valley in the land of Shinar and settled there.
References for Genesis 11:2
They said to each other, "Come, let us make oven-fired bricks." They had brick for stone and asphalt for mortar.
And they said, "Come, let us build ourselves a city and a tower with its top in the sky. Let us make a name for ourselves; otherwise, we will be scattered over the face of the whole earth."
Then the Lord came down to look over the city and the tower that the men were building.
The Lord said, "If, as one people all having the same language, they have begun to do this, then nothing they plan to do will be impossible for them.
Come, let Us go down there and confuse their language so that they will not understand one another's speech."
References for Genesis 11:7
So the Lord scattered them from there over the face of the whole earth, and they stopped building the city.
Therefore its name is called Babylon, for there the Lord confused the language of the whole earth, and from there the Lord scattered them over the face of the whole earth.
References for Genesis 11:9