Council of Nicea 325 CE
Now we come to a classic example of "translator's nightmare". And this one of the best!
To put it all in context, the "Nicene Creed" was written in Greek by the Fathers at the Council of Nicea in 325. It begins "pisteuomen" - "We believe...", and is intended to be a statement of the beliefs of the Church against the various "heresies" prevalent at the time. It was never meant to be recited as a prayer or a confession of Faith.
"Credimus in unum Deum....consubstantialem Patri...."
The Greek term used for what we understand as "consubstantial" was "homoousion" - "homoousion" - this means (literally) "same stuff" - "Stuff" could be translated as "substance" but we rapidly get into a circular argument. It is intended to convey what the relationship among the Divine persons of the Christian Trinity is and connotes that God the Father, God the Son, and God the Holy Spirit are "of one being" in that the Son is "generated" ("born" or "begotten") "before all ages" or "eternally" of the Father's own being, from which the Spirit also eternally "proceeds." It is also meant to convey that Jesus is "consubstantial" of "one substance" with us! He is truly man as well as truly God.
In the council of Constantinople in 381 the Greek form of the Creed was maintained with some changes to counter a few more heresies - "homoousion", "homoousion" was retained.
By 390, when the first Latin version appears, the translators had a problem - the Greek term had no equivalent in Latin! Greek grammer is far more extensive than Latin and there wasn't a single word which expressed the "sameness" of the Father and Son in both space and time! At first the phrase "eiusdem generis" was used - "of the same kind". This didn't really work. You could ask the question "same kind of what?" Eventually (by the year 451 and the Council of Chalcedon) the phrase "consubstantialem" appears. It is a made-up word - "con"="of the" and "substantia"= "(same - the word is assumed) stuff". Classical Latin has no need of the phrase "of the same stuff" in the Theological context in which it arose.
The term has been argued over ever since! Nothing effectively conveys what is meant in the spatial and temporal relationship of the persons of the Trinity (will we ever know this side of the Parousia?) The most recent translation has gone back to the original Latin as being more faithful in translation than "of one being" - trouble is, we don't often use the word "Consubstantial" in 21st Century language!!! So God knows what it means!!!
To give a couple of modern examples, what does the word "understand" mean? Is it, "know about" or "have experienced"? What does the word "nice" mean? Is it "a fine distinction" or "something pleasant"?
Finally, the version we now use "Credo" - "I believe" is the version adopted by the Eastern Byzantine Church, we inherited it and then, briefly, went back to the original "Credimus" - "We believe" prior to the new translation - now we are back to the Byzantine version!