Greek "to tame"

Sts. Cosmas  and Damian were brothers, born in Arabia, who had become eminent for their skill in the science of medicine. Being Christians, they were filled with the spirit  of charity and never took money for their services. At Egaea in Cilicia, where they lived, they enjoyed the highest esteem of the people. When the persecution under Diocletian  broke out, their very prominence rendered them marked objects of persecution. Being apprehended by order of Lysias, governor of Cilicia, they underwent various torments about the year 283. Their feast day is September 26th. They are patron saints of pharmacists.

As early as the 4th century, churches dedicated to the twin saints were established at Jerusalem, in Egypt and in Mesopotamia. Theodoret records the division of their relics. Their relics, deemed miraculous, were buried in the city of Cyrrus in Syria. Churches were built in their honor by Archbishop Proclus and by Emperor Justinian I (527–565), who sumptuously restored the city of Cyrus and dedicated it to the twins, but brought their relics to Constantinople; there, following his cure, ascribed to the intercession of Cosmas and Damian, Justinian, in gratitude also built and adorned their church at Constantinople, and it became a celebrated place of pilgrimage. At Rome Pope Felix IV (526–530) rededicated the Library of Peace (Bibliotheca Pacis) as a basilica of Santi Cosma e Damiano in the Forum of Vespasian in their honour. The church is much rebuilt but still famed for its sixth-century mosaics illustrating the saints.

What are said to be their skulls are venerated in the convent of the Clares in Madrid, where they have been since 1581, the gift of Maria, daughter of Emperor Charles V. They had previously been removed from Rome to Bremen in the tenth century, and thence to Bamberg (Matthews). Other skulls said to be theirs have been discovered at Easter 1334 by Burchard Grelle, Prince-Archbishop of Bremen. He "personally 'miraculously' retrieved the relics of the holy physicians Cosmas and Damian, which were allegedly immured and forgotten in the quire of the Bremen Cathedral. In celebration of the retrieval Archbishop and Chapter arranged a feast at Pentecost 1335, when the relics were translated from the wall to a more dignified place." (For the original quotation see the note) Grelle claimed the relics were those Archbishop Adaldag brought from Rome in 965. In about 1400 the cathedral master-builder Johann Hemeling commissioned a shrine for the relics, which has been accomplished until after 1420. The shrine from carved oak wood covered with gilt rolled silver is considered an important mediaeval gold work. In 1649 Bremen's Chapter, meanwhile Lutheran, sold the shrine with the alleged relics to Maximilian I of Bavaria. It is now shown in the Jesuit church of St Michael in Munich. At least since 1413 another pair of skulls is stored in St Stephens's Cathedral in Vienna.

The martyr twins are invoked in the Canon of the Mass in the prayer known as the Communicantes (from the first Latin word of the prayer): "In communion with the whole Church, they venerate above all others the memory of the glorious ever-virgin Mary, Mother of our God and Lord, Jesus Christ, then of blessed Joseph, husband of the Virgin, your blessed Apostles and Martyrs, Peter and Paul, Andrew, James, John, Thomas, James, Philip, Bartholomew, Matthew, Simon and Jude: Linus, Cletus, Clement, Sixtus, Cornelius, Cyprian, Laurence, Chrysogonus, John and Paul, Cosmas and Damian and all your Saints: grant through their merits and prayers that in all things we may be defended by the help of your protection." They are also invoked in the Litany of the Saints.
The martyrdom of Saints Cosmas and Damian by Fra Angelico (Musee du Louvre, Paris).

Their feast day in the Roman Catholic calendar of saints, which had been on September 27, was moved in 1969 to September 26, because September 27 is the dies natalis ("day of birth" into Heaven) of Saint Vincent de Paul, now more widely venerated in the Latin Church, but some traditionalist Catholics continue to observe the pre-1970 calendar.

Sts Cosmas and Damian are regarded as the patrons of physicians and surgeons and are sometimes represented with medical emblems.

Sir William Hamilton (1730–1803) reported that, among the wax representations of body parts then presented as offerings to the two doctor saints at Isernia, near Naples, on their feast day, those of the penis were the most common.[8] They were in fact venerated as patrons of "young girls anxious for a husband, and married women desirous of children."[9]

In Brazil, the twin saints are regarded as protectors of children, and September 27 is commemorated, especially in Rio de Janeiro, by giving children bags of candy with the saints' effigy printed on them. Saint Cosmas and Damian Church, in Igarassu, Pernambuco is Brazil's oldest church, built in 1535.