Pope Benedict imposing the pallium
On the feast of Saints Peter and Paul the Holy Father gives the sacred pallium to the world's newest archbishops. What is the pallium? Where does it come from? What does it signify.
The word pallium is Latin for a traditional Roman cloak made from wool. It is a garment that only the Pope can confer and signifies the jurisdiction of a metropolitan archbishop and also the special communion that the recipient shares with the Pope and the Church of Rome. The earliest reference to the pallium derives from the reign of Pope Marcus (died 336) who conferred the pallium on the bishop of Ostia.
The pallium is still made from lamb's wool. In fact, the lambs are are a gift from Trappist monks. The wool is then given to the nuns of the convent of Saint Agnes who weave the wool into the pallia. (The Latin word for "lamb" is agnus and this has long been a pun associated with Saint Agnes.) The connection with sheep also recalls "Christ the Good Shepherd" who carries the wandering sheep upon His shoulders. Similarly, the pallium is a reminder to the archbishop that he too should be a good shepherd ever mindful of the straying sheep. He is called to carry the sheep on his shoulders.
Last of all, the finished pallia are then placed over the relics of Saint Peter in the Vatican. Thus, each pallium is a third class relic of Saint Peter. So the Archbishop, when he wears his pallium is wearing a relic of Saint Peter!
So the pallium has a twofold symbolism. First is symbolizes that the archbishop carries the sheep on his shoulders. Second, it signifies his union with Saint Peter's successor, the Bishop of Rome.