Based on the facts presented in The Riddle of the Rosetta Stone, the rock slab is called the "Rosetta Stone” because it is named

in honor of a famous Egyptian pharaoh.
in honor of the mother of Napoleon.
after the French army officer who uncovered it.
after the town near where it was discovered.

I'd guess that it would be hard to read a paragraph in any article on this topic and not find the correct answer. Have you actually read any of your assignments?