I know what that means! I didn’t learn this latin in private school though. Mad Michael Savage (himself!) translated this for me and other radio listeners years ago. It means “Don’t Let The Bastards Grind You Down!”
The Latin saying is also rendered as “Ne illegitimi non te carborundum”
(Double negative is correct in Latin, plus the second person singular as direct object).
“Semper ubi sub ubi”
;^)