If you want to study music, you have to learn some Italian. Can you say adagio, andante, allegro? If you want to be a ballet dancer, you need to learn some French to know how to say and execute a pas de deux, plié, and brisé. People all over the globe today need to learn a little English to be able to navigate the internet.
Most of the English-speaking world received its Christianity from Western Europe, where for a millennium and a half all worship services and most education was required to be conducted in Latin. And so it is not surprising that quite a bit of Latin terminology has persisted in church talk. Don’t fight it. Learn it. It is efficient shorthand. The Magnificat is the song of Mary from Luke chapter 1. The Agnus Dei is a liturgical song just before Lord’s Supper that echoes the gospel message of John the Baptist. The Gloria in Excelsis Deo is the song of the angels on Christmas Eve.
If the church is going to use its historic vocabulary, however, it needs to take seriously the need regularly to teach and explain so that its talk doesn’t become frustrating jargon to newcomers. Those who know always need to bring more people into that knowledge. Like the evangelist Philip: The Ethiopian asked Philip, “‘Tell me, please, who is the prophet talking about, himself or someone else?’ Then Philip began with that very passage of Scripture and told him the good news about Jesus” (Acts 8:34,35).