Stereotype - etymology

The term stereotype (στερεότυπος) derives from the Greek words στερεός (stereos), "firm, solid" and τύπος (typos), "impression", hence "solid impression".

Movable type meant that instead of carving the block, the negative image as it were, could be thrown together from a pile of little pieces. Much faster. But still time consuming and with only a single printers plate to use. Doing enough printing with this meant wear and tear on the type and one would have to start again. Firmin Didot was a member of a large and important family in the world of European printing and it was his idea that instead of making up a plate or block out of movable type and then going straight to press, one could first slather the block with plaster or papier-mâché and pull off a negative of the negative. This was called a matrix. The matrix could then be plopped into molten lead and multiple copies of the printing plate made, not only reducing the concern about wear and tear, but also allowing parallel print runs on several presses.

The resulting plate was of course a solid chunk covered with the type. In Greek the word for solid is stereo, hence stereotype. When we think that for instance all politicians are the same, we say that opinion is a stereotype, and the meaning comes from the printing industry where all printings should have been the same off of the multiple plates made in this way.