The thing that's always confused me about supernumeraries is that they never seem to be either super or numerous.
Still, never mind.
Word To Use Today: supernumerary. The super bit comes from the Latin word for above, and the num bit comes from the Latin numerus, which means number.
Supernumerary means more than usual or more than necessary, and it will often refer to a temporary assistant, or anyone one who isn't really required.
It can also be used to describe an actor with no lines to say, especially if he or she is unpaid.
The House of Lords by Thomas Rowlandson, Augustus Charles Pugin, John Bluck, Joseph Constantine Stadler, Thomas Sutherland, J Hill and Harraden...
...and what they all did is anyone's guess.