Tetragrammaton was not a name, it is a way to say four letters in hebrew.
Many jews considered the four letters "YHVH" too holy too speak. They feared using God's name with a mistaken word or meaning before or after it in speech or writing could be considered blasphemy.
The jews took this verse very seriously, and dared not chance the possibility.
Exodus 20:7
"You shall not take the name of the Lord your God in vain, for the Lord will not leave him unpunished who takes His name in vain."