Kyrie eleison
From Conservapedia
Kyrie eleison is the first part – an acclamation – in the Latin Mass Ordinary, sung immediately after the entroit. It consists of nine statements: “Kyrie eleison” three times; “Christe eleison” three times; “Kyrie eleison” again three times. (“Lord, have mercy…Christ, have mercy…Lord, have mercy.”) The Greek text, “Kyrie eleison” was established in both the Eastern and Western churches from the earliest times. Pope, St. Gregory the Great is thought to have added the “Christe eleison”, thus creating the present form.