Well, since you didn't give me any context clues, I'm just gonna figure it out on my own!
So, obeisance sounds like, since the late middle english word obeisance also ties in with obedient, I would say that obeisance means to pay submission to, or give, like a sign of respect, so doing a bow or curtsy would be what I'm thinking of.
The patricians were the wealthy upper class people. Everyone else was considered a plebeian. The patricians were the ruling class of the early Roman Empire.
