Now it seems that this may have begun with a mistaken conclusion. Dutch classicist, Christine Mohrmann, in a long series of articles and books in all the main European languages, demonstrated that Liturgical Latin (and, before it, Liturgical Greek) were never really vernacular.
"Liturgical Latin, as constituted towards the end of Christian Antiquity and preserved unchanged - in its main lines at least - is a deliberately sacral stylisation of Early Christian Latin as it gradually developed in the Christian communities of the West. The Latin Christians were comparatively late in creating a liturgical language. When they did so, the Christian idiom had already reached full maturity and circumstances rendered it possible to draw, for purposes of style, on the ancient sacral heritage of [pagan] Rome ... As regards the plea which we hear so often for vernacular versions of the prayer texts, I think ... that we are justified in asking whether, at the present time, the the introduction of the vernacular would be suitable for the composition of sacral prayer style. As I have pointed out, the early Christian West waited a long time before adopting the use of Latin. It waited until the Christian language possessed the resources necessary to create an official ecclesiastical prayer language. ... the modern, so-called Western languages ... are less suitable for sacred stylisation. And yet we must realise that sacral stylisation forms an essential element of every official prayer language and that this sacral, hieratic character cannot, and should never, be relinquished. From the point of view of the general development of the Western languages - to say nothing of the problems raised by other languages - the present time is certainly not propitious for the abandonment of Latin".While Lutherans have long been comfortable with the vernacular, we did keep an archaic form of English (commonly called King James English) for a very long time -- to the 1970s! One of the very urgent causes for changing to modern English (and a fairly common form of English) was the presupposition that the language of the liturgy should be primarily understandable and preferably the language used in ordinary speech. So we ditched the Thees and Thous and the longer endings to verbs and even terms that had been used since the time of the Reformation (at least in England) and gave up the borrowed words from Greek and Hebrew (Sabaoth became power and might). Along with this is the presumption that Lutherans got rid of Latin right away as if it were yesterday's newspaper. Joseph Herl in his Worship Wars in Early Lutheranism debunks the myth that Lutherans went quickly into the vernacular and congregational song.
My point is this, liturgical language is never the common language of man but is always the specific and directive language of Scripture and the nature of worship compels us to use an often stilted or out of date form of the vernacular (at least judged by those outside the church). I am not at all suggesting that we adopt Latin but rather challenging the idea that liturgy must use the common and ordinary forms of language. The goal of worship, after all, is not to bring the liturgy down to its common denominator but to bring the people into the presence of God (through Word and Sacrament). Where God is there is always the holy ground wherein we stand but not as a people who have a right but always through the privilege of grace. Nothing detracts from this presence more than the idea that God and His grace can be reduced to simple, ordinary, and common things. Our Lord may use common elements (water, bread, and wine) but they are given to us with the uncommon grace of His will and purpose that delivers what is signed. Language itself does this. Luther once remarked that it was not easy to teach God German. It might also be said that we must be taught the language of God.
HT Father Hunwicke