So, that plate that I found at the National Museum of Scotland was fascinating, and I looked into it further. Wikipedia to the rescue, and the Museum of Printing.
This is a Stereotype, and is actually the root metaphor for the idea of repeating the same thing over and over with minor variations, “cliché” is another word for this object (also simply a stereo or a stereoplate)
Cliché is french onomatopoeia, it refers to the sound that the molten lead makes when it hits the moveable type plate to cast the stereotype printing plate.
While modern printing of newspapers is a complicated process, it used to be even more time consuming, so, it made sense to set commonly used words or phrases in moveable type and cast them as one piece of metal so that setting them by hand into the moveable type plates would be faster. Hence the modern use of the word cliché to mean something that is repeated so often that it is predictable and betrays lack of original thought.
It is often interesting to look back and see language re-embodied, to see the physical processes that inform the way we speak. The metaphors we use really inform the way we think about the world, and so often we don’t even realize when we are using a metaphor as a tool for thinking they are often so deeply and culturally trained that we see them as natural or logical and don’t even know that they have roots and histories that can be questioned.