I was reading Archbishop Fulton Sheen's Life of Christ and he always refers to Isaiah and Isaias and Elijah as Elias.
I know that's one of the traditional English spellings, but when did it change for Catholics at Mass (at least in Latin translated Missals) and in other liturgical use?
Not on topic here, but well appreciated would be an explanation of how one could come to pronounce -jah as -ias.
I think you'll find the question is not how -jah came to be -ias as how -ias came to be -jah.
For example you could look at the Greek rendering of the name Isaiah as see that it is Ἠσαΐας (pronounced Ēsaïās) which is a pretty clear indication that at one significant point in history the name was pronounced closer to the old/alternate English rendering of Isaias.
In general you will find names mutilated morphing from language to language and in a language over time as it gets to some persons ears and doesn't sound quite right. It's quite possible that at some point an Englishman's ear told him that ending a name with -ias sounded foreign and so he adapted it, however...
Pushing farther back however you will find the Hebrew name was יְשַׁעְיָהוּ (Yəšạʻyā́hû) so it might be that the more modern English rendition is actually an attempt to render an English name closer to the original rather than following the long tail of languages in between.
A similar story can be told for Elijah who's Hewbrew name would be אליהו (Eliyahu) but in much more modern usage is rendered إلياس, in Arabic (Pronounced Ilyās).
As for WHEN the change happened, it would see that for Isaiah, Isias might actually be a trendy thing started by a couple of writers in the mid 1900's. However the majority usage dating back to at least the 1600's KJV text is undoubtedly "Isaiah".
The Latin Vulgate, which was translated by St. Jerome from Hebrew and Greek originals, used -as rather than -ah as a suffix for certain Hebrew names (apparently those ending in -yah in Hebrew). The choice was apparently made because -as is a relatively common Greek and Latin word ending—Greek and Latin, being highly inflected languages, generally prefer standardized noun endings.
The forms of Old Testament names remained in the Latin Vulgate, and subsequently into the Nova Vulgata, the revision of the Vulgate still used for Latin Scriptural texts in the Church and available on the website of the Vatican. The form Isaias, for example, appears in the translation of Isaiah 2:1
Verbum, quod vidit Isaias filius Amos super Iudam et Ierusalem.
[The word, which Isaiah, son of Amos, saw regarding Judah and Jerusalem.]
Forms ending in -as were taken over into Catholic (and also Protestant) translations into English. The Tyndale Bible, for example, begins the book of Jonah:
The worde of the lorde came vn to the prophete Ionas ye sonne of Amithai sayenge:
(Jonah 1:1; emphasis added)
The first specifically Catholic translation of the Bible into English was the Douay-Rheims Bible, which was published between 1582 (New Testament) and 1610 (Old Testament), and primarily taken from the Vulgate (with consideration given to the Hebrew and Greek). The Douay-Rheims renders Jonah 1:1
Now the word of the Lord came to Jonas the son of Amathi, saying:
The Douay-Rheims Bible appears to have been the official Catholic English-language edition of the Bible until the mid-20th century or so (it was supplanted by the Jerusalem Bible in 1966 and the New American Bible in 1970). Certainly it was the translation with which most English-speaking Catholics would have been familiar. That would explain its use by Archbishop Sheen.
The newer Jerusalem and New American Bibles use the original Greek and Hebrew as their primary sources, and have -ah as the ending for these names. The National Council of Catholic Bishops (now the United States Council of Catholic Bishops) adopted the New American Bible as the standard for the 1970 English-language Lectionary adopted after Vatican II, and since then the names have been referred to with this ending.
