Below is a research-style paper analyzing the meaning, history, and significance of the word "Sator" within that context.

In this context, "Sator" became synonymous with God the Creator (The Sower of the Word). The phrase "Sator Arepo" was thus viewed as a hidden declaration of Christian faith during times of persecution.

Since the word rarely appears in modern English as a standalone noun, it is most likely that you are referring to the famous Sator Square (or Rotas Square), an ancient Latin word puzzle.