Here's why it's called "Key":
* Black is the key color in four-color printing. It's used to create deep blacks and rich shades.
* It's also used to separate colors for printing. The "key" plate in the printing process is the one that carries the black ink.
CMYK is a color model used in printing, where:
* C stands for Cyan
* M stands for Magenta
* Y stands for Yellow
* K stands for Key (Black)