E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Dionysius (the younger),
being banished a second time from Syracuse, retired to Corinth, where he turned schoolmaster for a living. Posterity called him a tyrant. Byron, in his Ode to Napoleon, alludes to these facts in the following lines:
Corinths pedagogue hath now
Transferred his byword to thy brow.
That is, Napoleon is now called tyrant, like Dionysius.