Our term “liturgy” comes from the Greek term leitourgeo. In non-biblical Greek this term carries the connotation of that of service rendered toward the city as a good citizen or as service to the deity in religious contexts. In the Old Testament, it mostly refers to the activities of the priests in connection with service at the temple or in carrying out religious duties.
In the New Testament, it is used very similarly as referring to the priestly ministry of the OT. Paul even connects the immanent end of his life to “priestly” language in Phil. 2.17 – “But even if I am being poured out like a drink offering on the sacrifice and service (leitourgia) coming from your faith…” There is also the sense of an act of service like giving to the collection for the saints (Rom. 15.25; 2 Cor. 9.12) as “service” (or the noun form of leitourgeo). There is a further movement toward internal spiritual acts as seen in Acts 13.2 – “While they were worshiping (participial form of leitourgeo) the Lord and fasting, the Holy Spirit said…”
The infrequent use of the term in the NT is connected partly with the OT. The end of the OT religious system due to the work of Christ means that the terms connected with the priestly, “official” system are not relevant to the priesthood of all believers.
When comparing the "official" Christian ministry with that of the OT priests opens the door for a more specific use of the term connected to the ministry of overseers or bishops (see the writing of the Apostolic Father Clement, 1 Clement 40ff.) In this way the term finally came to be used of Christian religious practices, especially communion, as they were overseen by an “officiant”, giving us the common meaning of “liturgy.”