Jon answered your question well-enough, but I could add this:
In a scripture class I took (the priest was a renown scripture scholar),
I recall someone asking
Why does scripture say "I love Jacob. But I hate Esau" ?
The professor went on a bit of a rant, actually.
He said "hate" is a poor translation. Like Jon posted above, we translate words as best we can. In this case, "hate" actually meant "preferred less"-
"Hate" and "preferred less" sounds like a very strong deviation to me, wouldn't you say? But at one time that's what "hate" generally meant: to prefer less. So, for it's day, it wasn't mistranslated. The problem with old translation is subtle. Everyone thinks they are most faithful translations, and surely they may have been, but as time goes along- modern words change meaning. So, with time, you have to keep checking the current meaning of words!
So, you can see why people could have translated it this way "hate"
Yet, the professor still questioned why they settled on "hate"
He also explained that "vengeance is mine" is not accurate. He believed, again, it should have been translated "righteousness is mine"
Wow- how many people have lost their faith because of this mistranslation! Thinking God is truly "vengeful"! No, he said, in the original language, that this indicated a desire on God's part for OBJECTIVE FAIRNESS towards each. "Vengence is mine" might have been more accurately translated as "the desire of God for fairness in the objective order", he said.
Yikes, a bit long! You can see why the opted for the shorter "vengence", but at what cost to souls?
You could say "vengence" was a "poor translation", unfortunately one that has caused many to lose faith in the goodness of God!