Hello, Dylan.  :smile:

Well, I'm not a Bible expert, but I know a thing or two about the Bible I guess.

When St. Jerome translated the Bible into the Latin Vulgate, he used manuscripts that we no longer have. The Septuagint was translated from Hebrew itself, and Greek would have, of course, had different sorts of words and meanings. St. Jerome translated using both Hebrew and Greek manuscripts. He also even would have used a copy of St. Matthew's Gospel in the original Aramaic/Hebrew, or native Hebrew tongue in the first century.
Now the Douay-Rheims was translated using the Latin Vulgate, but Hebrew and Greek manuscripts were also consulted. So, my guess then would be there was a leaning on the Masoretic text when translating. Here is a site I know of about the Douay-Rheims: www.douaybible.com.
If you know already, I wonder now to be sure, is the Masoretic text a Hebrew text that came later on after the first century?