16/17th Century skull with Sator Square
The Sator Square is a word square containing a Latin palindrome featuring the words SATOR AREPO TENET OPERA ROTAS written in a square so that they may be read top-to-bottom, bottom-to-top, left-to-right, and right-to-left.
One likely translation is “The farmer Arepo has [as] works wheels [a plough]”; that is, the farmer uses his plough as his form of work. Although not a significant sentence, it is grammatical; it can be read up and down, backwards and forwards.
If “arepo” is taken to be in the second declension, the “-o” ending could put the word in the ablative case, giving it a meaning of “by means of [arepus].” Thus, “The sower holds the works and wheels by means of water”
The Sator Square is a four-times palindrome, and some people have attributed magical properties to it, considering it one of the broadest magical formulas in the Occident. An article on the square from The Saint Louis Medical and Surgical Journal vol. 76, reports that palindromes were viewed as being immune to tampering by the devil, who would become confused by the repetition of the letters, and hence their popularity in magical use.
source: The Macabre And the Beautifully Grotesque