Could you explain why the celebration of the Eucharist is called in the Latin Church “Holy Mass” and in the Eastern Churches “Divine Liturgy,” and whether the two terms may be used interchangeably?
The word “Mass” refers properly only to the Eucharistic Liturgy of the Latin Church. The word has its origins in a dismissal found only in this liturgy. At the end of the celebration, the priest says (in Latin) “Ite missa est.” This can be roughly translated as “The dismissal is made.” In time the word “missa” was used to designate the entire Latin liturgy, and the word began to be pronounced as “Mass” by the laity.
In the Eastern Churches, the Liturgy is properly referred to as the “Divine Liturgy.” Liturgy is a Greek word, meaning “the work of the people.” Literally, Divine Liturgy means “the heavenly work of the people.” In the Eastern Liturgies there is a strong sense that the congregation has left this world, and is being mystically transported to heaven, where we participate in the Heavenly Liturgy. That is why we don’t use musical instruments.
It really is not correct to use the two terms interchangeably, although it sometimes happens.