Simplify the following text for a Grade 9 native English-speaking person.
Original: The varying corpus denoted Aesopica or Aesop 's Fables includes most of the best-known western fables , which are attributed to the legendary Aesop , supposed to have been a slave in ancient Greece around 550 BCE .
Simplified: The most famous fables are those attributed to Aesop ( 6th century B.C. ) .