Where does utrinque paratus come from for the parachute regiment motto?

Utrinque Paratus is Latin and means "Ready for both." The phrase was first used by the British Army's Parachute Regiment in World War II. It was chosen because it encapsulates the regiment's ethos of being ready to fight on both sides of the enemy lines, if necessary. Utrinque Paratus has been the regiment's motto ever since.