Graecus

Okay kiddo, so "graecus" is a word that means "Greek" in Latin. You know how some people speak different languages, like how your friend's family speaks Spanish at home? Well, in ancient times, Greek was a really important language that a lot of people spoke and wrote in. So when people in ancient Rome wanted to talk about things related to Greece or Greek culture, they would use the word "graecus" to mean "Greek." It's kinda like how we use the word "Mexican" to talk about things from Mexico. Does that make sense?