RALPH: Decius Brutus is making a reference to religious practices that existed in Shakespeare’s England, not ancient Rome. In early Christian times, when religious martyrs or saints died, parts of their bodies, as well as items such as the cross on which they had been crucified, were preserved as objects of worship. These are referred to as relics.

SERVILIA: In Shakespeare's Protestant England, Catholicism was officially banned, and sometimes Catholic priests would be publicly executed. At these executions, faithful Catholics would press forward to stain their handkerchiefs with the martyrs’ blood to keep as relics. In his interpretation of Calpurnia’s dream, Decius Brutus is imagining noble Romans pressing forward to get a relic stained with Caesar’s blood.

RALPH: The word “cognizance” derives from the Latin word meaning to know, and that’s how we use it today – to have cognizance of something means to know about it. But in Shakespeare’s time, a cognizance was an emblem worn by a servant indicating the noble household where the servant was employed. In these lines, Decius Brutus is evoking an image of Romans wearing their blood-stained relics as emblems of their loyalty to Caesar, just as the English Catholics sometimes did to express their religious faith.