Brutus was also a
pseudonym used by the "anti-federalists" early in the history of the
United States. The "anti-federalists" as their
name implies wanted a less centralized
government where
individual states would have more power.
Rather than publish opinions under their own name, the framers of the constitution sent essays anonymously to local newspapers to convince the public that their way was better. Alexander Hamilton and James Madison, most famously, published under the pen name "Publius" what became the "Federalist" (commonly called "the Federalist Papers") later with John Jay.