The Rotas Square (or Sator Square) is a word square containing a Latin palindrome. By repositioning the letters around the central letter ?; a Greek cross can be made that reads Pater Noster (Latin for 'Our Father'; the first two words of the Lord's Prayer) both vertically and horizontally. The remaining letters - two each of A and O - can be taken to represent the concept of Alpha and Omega; a reference in Christianity to the omnipresence of God.

The square was likely used as a covert symbol for early Christians to express their presence to each other.