The word "Liturgy" refers to the Christian remembrance and celebration of Jesus Christ's propitiatory sacrifice of His body and blood. Also known as the service of the Eucharist, the Liturgy is central to any Christian order of worship.
"And He took bread, gave thanks and broke it, and gave it to them, saying, 'This is My body which is given for you; do this in remembrance of Me.' Likewise He also took the cup after supper, saying, 'This cup is the new covenant in My blood, which is shed for you'" (Luke 22:19-20).
The Liturgy was composed by the Apostles as taught to them by our Lord Jesus Christ, who after His resurrection appeared to them, "To whom He also presented Himself alive after His suffering by many infallible proofs, being seen by them during forty days and speaking of the things pertaining to the kingdom of God" (Acts 1:3).