Explanation: In Ancient Rome, traitors and tyrants of sufficiently vile reputation would posthumously have their names removed from their achievements - a big deal to the Romans, who regarded names and dedications as a way of living on after death by one's deeds. Inscriptions would be carved over, statues broken, coins reminted. Everything that could be done to 'write them out' of the official achievements of state during their reign - after all, being remembered by the Res Publica is an honor, not a right! This process is called Damnatio Memoriae in the modern day, though it could go by several different terms in the sources.
While it was not meant to literally erase their memory from existence, just remove any of the honors granted to them, however marginal, during their reign, it is a bit funny that we remember such Emperors still.
The rate of damnatio memoriae was... remarkably high during the tumultuous Crisis of the Third Century, wherein constant coups and civil wars resulted in a high turnover of Emperors - and often bad feeling between the sitting Emperor and his predecessor!