@jhine
You don't know if the apostles didn't include Jehovah or equivalent in their wrings as the original manuscripts no longer exist. Apostasy crept into the christian congregation pretty soon after the last of them died and by the 3th century the teaching of the trinity was in full swing. The oldest known NT manuscripts are about 150 years after the last of the Apostles died. These do not have the divine name in them. In fact apparently there are no existing NT manuscripts with the divine name, not even where quotes are made from the OT where the name does appear, which is very strange. This is the reason why some scholars such as prof. George Howard believe that the divine name WAS included in the original writings of the apostles, because when you are quoting a scripture (from the OT) where the divine name obviously appeared (as in the dead sea scrolls) then the same name should appear in your quote otherwise it wouldn't be a quote. Another scholar ( Prof. Wolfgang Feneberg) makes a logical observation "He [Jesus] did not withhold his father's name YHWH from us, but he entrusted us with it. It is otherwise inexplicable why the first petition of the Lord's Prayer should read: 'May your name be sanctified!.........in pre-Christian manuscripts for Greek-speaking Jews, God's name was not paraphrased with kýrios [Lord], but was written in the tetragram form in Hebrew or archaic Hebrew characters. . . . We find recollections of the name in the writings of the Church Fathers".
In any case, your argument that including the name Jehovah in the NT means a word was added is not true, a noun was substituted with a name. Nothing was added.