After discussing it with a friend of mine, my understanding of it is this:
There was really no officiall title at all, and emperors chosed the name they preffered and implemented it into their name, and not a title. These names include : Augustus, Caesar & Imperator. Because the first emperor known as "Augustus" changed his name several times from:
Gaius Julius Caesar Octavianus (Adopted by Julius Caesar, but kept his last family name)
Gaius Julius Caesar Octavianus Augustus (He was given the title Augustus)
Gaius Caesar Divi Filius Augustus (Son of God aka Son of Julius Caesar - he was seen as a god?)
Imperator Caesar Divi Filius Augustus (Added Imperator to his name, meaning "Commander" of sorts)
And later emperors, both inside the Roman Empire and outside of it (Russian, HRE etc) chosed the names they liked the most, or the ones they thought was the most "right". Therefore we see all of them at different time periods, until one ultimately won and become an official title. Other empires also chosed what they preffered when they become an empire:
Russian = Tsar (From Caesar)
German = Kaiser (From Caesar)
French = Empereur (From Imperator, idk if it was early Franks or later French aka Napoleon?)
English = Emperor (From Empereur, which is from Emperator.)
In the Roman Empire we could see some emperors using 2, if not all 3 titles at the same time, as at this time, it was just names, not titles.
Can I assume all of this is correct?
"Caesar" was originally just a family name, the
nomen of a patrician family of Rome belonging to the
gens Iulia, known as the
Iulii Caesares.
When Julius Caesar was murdered in 44 BCE he was childless, and he left in his will as his universal heir his grandnephew
Gaius Octavius Thurinus, a member of an equestrian branch of the plebeian
gens Octavia (Octavian's mother Atia was Caesar's nephew). The will also stated that Octavius had to become his uncle's adopted son as well as hir heir, so he (as was customary in Roman society) took the full name of his new "father",
Gaius Iulius Caesar Octavianus, although later he dropped the
Octavianus from his official name in order to distance himself even further from his origins.
With the acceptance of Caesar's will and his posthumous adoption, Octavian won a large amount of power, because he inherited not only Caesar's enormous fortune, but especially his immense political clientele, which included not only a large part of Rome's populace and ruling class, but most importantly the soldiers of Caesar's legions, who were related to Caesar by clientelar links as it was common in Roman society. Thus, it was key for Octavian's political ambitions to be seen as Caesar's rightful and legitimate heir as much as possible.
As all subsequent Roman rulers were either born of became "adopted" (in many cases posthumously) into the imperial house, all of them became
Caesares, either gaining that name by right of birth or adopting it after their "adoption" into the ruling family. Even emperors who rose to power by military force and who had no link whatsoecer with the previous ruler (like Vespasian) also played this charade by adopting the name
Caesar into their official imperial name. And in time, this name became the one by which foreign peoples came to refer to the Roman ruler. In the Gospels, the Roman emperor is referred to as "Caesar", and in the III century Middle Persian inscription of Shapur I at Fars, the Roman emperors are also named as "Caesars".
In 38 BCE, Octavian changed his name again and became
Imperator Caesar Divi Filius. He only retained the word
Caesar from his previous name (as it was its most important part, and still useful) and chose all the other words to further aggrandize his status in front of the Roman society.
Imperator was a title the Roman armies bestowed by
acclamatio onto a victorious commander, and
Divi Filius means literally "son of a/the god" or "son of a/the divinity"; by that time, Octavian had forced the Senate to deify his adoptive father Julius Caesar, and he immediately moved to exploit this action by calling himself "son of a god" in his new official name, copying a practice that had a long history in the eastern Hellenistic kingdoms. Thus, his third full officlal name could be translated as "The victorious commander Caesar, the son of a god".
And finally, in 41 BCE, after the victory at Actium, Octavian changed once more his full official name into its final form, and it became
Imperator Caesar Divi Filius Augustus, adding the adjective
augustus to it. In Latin,
augustus (
augustus, augusti) was originally an adjective meaning "majestic" or "venerable" and it was used traditionally to refer to the gods and their actions (its Greek equivalent was
sebastos). By adding it to his full official name, he emphasized even more his "sacred" aura, because from then on, he would be referred to with a term originally reserved to the gods.
The term mutated from an adjective into a name, and immediately
augustus became the equivalent of our modern title of "emperor"; the Roman emperor was always the
augustus, while there could be several
caesares (essentially, all the immediate family of the ruler). For an emperor to rise anybody else to the rank of
augustus, meant that he was sharing his power, and it was usually done by emperors with male sons, who wanted to ensure a smooth power transition after their death, although it could also be a political measure imposed by circumstances or random causes (Marcus Aurelius and Lucius Verus, Septimius Severus and Clodius Albinus or Pupienus and Balbinus).
The traditional way by which an usurpation attempt was launched in the Roman empire took place when gathered soldiers acclaimed their commander as
augustus, and the usurper minted coins calling himself
augustus.
