"Copy" is derived from the Old French word "copie," meaning "a copy."
"Cat" is derived from the Old English word "catt," meaning "a cat."
The combination of "copy" and "cat" likely emerged in the 19th century, drawing on the feline tendency to mimic behaviors. This combination effectively captures the idea of someone imitating another person's actions, much like a cat might mimic its owner.
Therefore, "copycat" is a playful and descriptive term that reflects the act of mimicking someone else's actions.