A recent argument involved two passages from Iasiah, 20:1 and 36:2:
When looking at the most modern translations and comparing them with older ones there is – as a tendency I presume – a glaring shift in translating two words:
תַרְתָּן and אֶת-רַבְשָׁקֵה
The KJV version renders the first as:
In the year that Tartan came unto Ashdod, (when Sargon the king of Assyria sent him,) and fought against Ashdod, and took it;
Whereas NIV – as an example – has:
In the year that the supreme commander, sent by Sargon king of Assyria, came to Ashdod and attacked and captured it--
Again an apparently similar phenomenon is found in 36:2. KJV:
And the king of Assyria sent Rabshakeh from Lachish to Jerusalem unto king Hezekiah with a great army. And he stood by the conduit of the upper pool in the highway of the fuller's field.
Then the king of Assyria sent his field commander with a large army from Lachish to King Hezekiah at Jerusalem. When the commander stopped at the aqueduct of the Upper Pool, on the road to the Launderer's Field,
So the tendency to observe is that an Assyrian/Akkadian word for a function or title was left untranslated, in my view, in the Hebrew text and in the old translation, like KJV.
But why do modern translations go for the translation of the function into modern language, when it seems as if the Hebrew text did no longer know about the specific function and seems to treat both words like proper names?
That these words are treated as proper names is claimed plainly, without proper citations, on this Wikipedia page: "In the Bible, the title is used as the proper name."
My reasoning within this translation issue was that the more literal translations are preferable than more modern (intended as helpful?) translations. תַרְתָּן in Hebrew is also rendered Tartan in the JPS version or here. I conclude from that that the textual composition history might give a clue: that by the time the text was finalised the functional title (like in 36:2) had lost its prior understanding to the then authors/redactors (of Isaiah, not KJV) and that thereby this transformed the word: crystallising it, into a proper name. Also compare this. Further research yielded me just fundamental etymology and the like but not real information on translation choices.