It comes from the nautical term "belay," which means to secure a rope. In the context of orders, "belay" signifies stopping or preventing the order from being carried out.
Here are some examples:
* Captain: "Fire the cannons!"
* First Mate: "Belay that order, Captain! There are civilians on board the ship!"
* Commander: "Advance to the next position!"
* Soldier: "Belay that order, Sir! We're facing heavy enemy fire!"
While the phrase is primarily used in a nautical context, it can be used in any situation where an order needs to be revoked or cancelled.