Burrus

• burro: (Spanish) donkey, ass. used figuratively as well to refer to something that is not very bright (synonym of the Italian 'tonto' meaning 'stupid, ugly'), and as a petty insult in gral.
• burro: (Italian) butter
• Burrus, Sextus Afranius : praetorian prefect, was advisor to Roman Emperor Nero and, together with Seneca the Younger, very powerful in the early years of Nero's reign.

As stated here [1] , the seemingly maieutic tone of the speaker may echo and parody E. Pound's beliefs and style and specially the beginning of his 'Canto XXI'

     Keep the peace, Borso! " Where are we?
         "Keep on with the business
                                      That's made me"

Few lines after 'Cosimo' (cfr. with 'Cassius') is introduced and, on top of that, there is another pertinent verse:

    And "with his credit emptied Venice of money"-