The title of Pater Patriae, or Father of the Country, was first given to a Roman general – Marcus Furius Camillus, in 386 BC. It was an honorary title conferred by the Senate, and in the case of Camillus, it was given because of his role after the siege of Rome in the Battle of the Allia by Gallic invaders, when he routed the Senones and was determined to be the second founder of the city, after Romulus. Roman imperial coinage
The title would not be used again for over three hundred years, when the Senate would confer it to consul Marcus Tullius Cicero in 63 BC, for his role in the exposing the Second Catalinarian Conspiracy to overthrow the Roman Republic by senator Lucius Sergius Catalina and various members of the senate and equestrian ranks. Cicero intercepted letters the conspirators sent to the Allobroges, a Gallic tribe, about the plot, read them to the Senate, and the Senate condemned the conspirators to death without a trial.
For having ended the civil wars, and declaring himself dictator and the de facto ruler of the Republic, the Senate next awarded the honor to Gaius Julius Caesar in 45 BC. However, the title for Caesar was Parens Patriae, or “Parent of the Country”, instead of “Father”. This was made possible by Caesar’s move in 46 BC to give himself the title Praefectura Morum, or “Prefect of the Morals”, allowing him to have the powers of a censor, but not subjecting himself to their checks and balances. As such, he was able to fill the Senate with allies, who then bestowed numerous honors and titles to him.
On February 5, 2 BC, the senate offered the title of Pater Patriae to Augustus. Although the title didn’t bring with it any additional powers, and wasn’t needed to legitimize his position as Roman emperor, it wasn’t used regularly in his list of titles. When it was used on coins, it was fully spelled out PATER PATRIAE. The coins stuck posthumously to honor Augustus often simply list the title as PATER.
The title would be offered to many subsequent rulers, some of which would accept the honor, but the tradition was to decline the offer initially out of humility, until the Senate would offer it again in the future. Tiberius declined the honor all-together and Nero declined it the first time. Hadrian deferred for eleven years, until finally accepting it in 128 AD. Nerva used the entire Pater Patriae on the reverse of an issue with sacrificial implements. Some of the emperors issued coins posthumously for previous rulers and included the Pater title. Many of the emperors with short reigns did not have the chance to prove themselves worthy to the Senate to have the title offered to them, but those that did would simply abbreviate it as P P on their coinage.