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You've completely misunderstood =)

For Kuzan, Sakazuki, and Borsalino - Aokiji, Akainu and Kizaru are not their aliases but their first names/surnames

no it isnt ye moron, that is called speculation

Yeah he's completely speculating, I think it's only to be more "feared".

They're not their surnames, they are really their aliases! Talking as a reader of the manga, these nicknames are related to the momotaro legend, but as a person in OP universe I agree with the theory of more fear for their enemies.