KYRIE ELEISON. — “Lord, have mercy!” is a Greek plea in both language and origin, used in sacred and profane contexts already in the ancient East among Greeks and Romans. It is frequently found (not always in the same form) in the Bible (especially in Psalms 6:3; 30:10; 40:5, 11; 55:2; 85:3; 118:29; 122:3; 133:2; Baruch 3:2; Matthew 15:22; 17:15; 20:30–31). It entered the liturgy no earlier than the late 4th century in Antioch (St. John Chrysostom, In Mt. hom., 71,4; PG 58,666; Hom. 6,1 in I Tim.: PG 62,530; Constitutiones Apostolorum, VIII, 6,4–9 c. 35, ed. Funk, I, 478, 480, 544) and in Jerusalem (Egeria c. 24: CSEL, 39,72). At Rome it was introduced toward the end of the 5th century, and by the time of St. Gregory I (d. 604)—perhaps even earlier by St. Benedict (d. 547)—it was recited alternately with “Christe eleison.” From Rome it spread to Gaul (Council of Vaison, 529), etc.; at Milan it had already been introduced earlier under Greek influence.
In the Eastern liturgy, the Kyrie is used as the people’s response to the deacon’s invitation in the litanies of supplication (ektenai); it is said without addition, separate from the other plea, but often repeated on other occasions.
In the Roman Mass it was recited in the form of the “Deprecatio Gelasii,” similar to the Greek chain, perhaps introduced into the “Missa catechumenorum” by Gelasius I (492–96) to replace the Oratio fidelium (omitted because intercessory prayers had been incorporated into the Canon), which is still used in the Ambrosian liturgy. Following the Roman example, St. Benedict arranged the “litaniae” for Lauds and Vespers; for the Little Hours he prescribed a shortened form, the “supplicatio litaniae,” consisting of Kyrie and, perhaps already alternated with “Christe eleison.” St. Gregory I himself distinguishes two forms: the greater in solemn Mass, the lesser in daily Masses, alternated with “Christe eleison” (Ep., 9,2, to Bishop John of Syracuse). The greater form was omitted; it no longer appears in the Roman Ordines. The number nine (documented in the Ordo of John Archicantor, ed. Silva-Tarouca, p. 196) was sometimes increased and ended at the pope’s signal. Later the sacred number nine (three times three) was fixed, interpreted by Amalarius as a tribute to the Most Holy Trinity, though in reality all the cries are directed to Christ. The shorter form occurs, outside Mass, in the Preces of the Office, and, placed at the beginning and end of the litanies, is repeated in processions. Outside liturgical use, especially in medieval France and Germany (Lais, Leisen), it was added to religious songs. It was recited or sung first by Greeks and Romans, between the deacon and the people; the celebrant did not recite it, but by the time of John Archicantor (Silva-Tarouca, p. 205) it was known that the priest recited it in private Masses (“... singulus... sacerdos... novem tantum vicibus”), and in sung or solemn Masses from the 13th century (Ordo Rom., XIV, nn. 61, 68, 71).
From the 9th century onward the so-called tropes began to be inserted, a custom that lasted until the reform of Pius V (1570).