This is one of those issues that has always bugged me.
Hebrew and Aramaic are both languages found within the Torah/Tanakh. If Hebrew is a divine language and given to us from Hashem as his word, why would we have occurrences where a separate language - Aramaic - is being used?
Wouldn't the argument that Aramaic is a sister language run against the claim that Hebrew is a divinely inspired/created language?
I was curious if the Rabbis ever wrestled with the issue. I genuinely struggle with this one.