Etymological history of the term brotus stems far back into the time of the Roman Empire. It is a modern day spin off based on the character description of Brutus, who was the famous assassin of Caesar. To be a brutus to someone is to stab them in the back and show no respect for them. Brotus is the antonym to the word brutus which, is a term that can be described as brotherhood. When someone is close friends with someone they are considered to be their brotus. The term brotus is the masculine version of term. The feminine version of the word is brotusette, and the plural masculine is brotusi.
John: "Is this guy you brought with legit?"
Sampson: "Oh yeah, he's my brotus, we go way back. He's good shit."