

When Megatron started his revolution he decided he needed to differentiate his faction, and so gave them a new name. In the Marvel comics continuity the Autobots were created by Primus and lived more or less peacefully on Cybertron. So this makes this continuity the only one were the Autobots and Decepticons were never the same race. Autobots as consumer grade machines, and the Decepticons as weaponized machines. In the 1984 cartoon continuity the two races were created separately by the Quintessons. Which, in essence, displays the philosophical differences between the two leaders.

When both Optimus Prime and Megatron rise up against the corrupt government, Megatron chose to name his faction with a new name and a new sigil, while Optimus decided to repurpose the term Autobot and derive it from "autonomous" (from the people, by the people) and keep the old sigil. Auto from automatons, because in the other races' eyes the Cybertronians were long lived mechanicals who never changed in any fundamental way (despite the name Transformers). In the IDW comics continuity the Autobot moniker is given to the corrupt Cybertronian Empire by the galaxy's other races to describe these mechanical beings. "Autonomous" as in deciding one's fate by themselves. In the Aligned continuity (which is the most similar to the Michael Bay movies), the term Autobot is coined by Orion Pax as a description for the concept of abolishing the caste system that the Cybertronians were living under, not as a description for the race as a whole. The rise of the term Autobot differs with each continuity.
