On the 20th of June in 1787, at the Constitutional Convention in Philadelphia, Oliver Ellsworth moved to confine legislative powers to two distinct branches, and to strike the word “national” from the document. Edmund Randolph of Virginia had previously moved successfully to call the government the National Government of United States. Ellsworth moved that the government should continue to be called the United States of America.
The final wording eventually became “All legislative powers herein granted shall be vested in a Congress of the United States, which shall consist of a Senate and House of Representatives.”
And, yes, the word “national” does not occur anywhere in the Constitution.