Shut up
What is the origin of the phrase "shut up"? I have been told that it refers to the visor being shut down/no further discussion and enter the battlefield; please help because I do not buy this definition.
It's mouths, not visors. From the Oxford English Dictionary, two early uses:
1826
"Let them answer the question, or shut up their mouths upon this subject."
1852
"Well, his mouth's shut up at last."