But what is it, specifically regarding the papal garment? From the Latin palla, "woolen cloak," it is currently a band of wool that wraps around a certain way for ceremonial occasions. It used to be longer, hanging lower, but has shortened over time. Mosaics at Ravenna and Rome show the pallium looking as it did centuries ago. In current practice, a pallium is blessed by Pope Francis on the feast of Saints Peter and Paul, but it will not be conferred then on a metropolitan archbishop: he shall receive it from the papal nuncio in his home diocese.
You may imagine that pallia are not bought at your corner ecclesiastical garment shop. It is made from the lambs who are presented by nuns of the convent of St. Agnes (a minor basilican in Rome). The wool is woven into the pallia by nuns of Santa Cecilia in Trastevere.
The significance of a garment of lambs wool draped over the shoulders of the pope may have originated with the pastoral image of a shepherd carrying a lamb draped over his shoulders. The popes are shepherds of their flock, etc.
Cæsarius of Arles was a pretty interesting character. He considered women the "gems of the Church." Unfortunately, like precious gems, he felt they should be locked away for safekeeping. I'll explain more in the next post.