Jewish worship and Gentile traditions underlie the early Christian Eucharist:
15. In gathering together to break the bread on the first day of the week, which became the day of the Lord (cf. Acts 20:7; Rv. 1: 10), the first Christian communities followed the command of Jesus who, in the context of the memorial of the Jewish pasch, instituted the memorial of his passion. In continuity with the unique history of salvation, they spontaneously took the forms and texts of Jewish worship and adapted them to express the radical newness of Christian worship.(Catechism 1096) Under the guidance of the Holy Spirit, discernment was exercised between what could be kept and what was to be discarded of the Jewish heritage of worship.
16. The spread of the Gospel in the world gave rise to other types of ritual in the churches coming from the gentiles, under the influence of different cultural traditions. Under the constant guidance of the Holy Spirit, discernment was exercised to distinguish those elements coming from “pagan” cultures which were incompatible with Christianity from those which could be accepted in harmony with apostolic tradition and in fidelity to the Gospel of salvation.
Not quite sure why the qualifier “those elements” is here; everything European and religious was pagan at the time. The only non-pagan world religions of the first century were in Asia. There is the influence of European mystery religions, I suppose.