I'm racking my brain with this question. I know that from the moment someone is able to learn a language they can interpret/translate/teach others. But how would that person go about it? Especially before written languages were created. If the languages were similar enough I suppose it wouldn't be that big of a deal, but what about those that were very different? I'm assuming children would have had a role in this if they lived somewhere with people from multiple nations. But how would someone set off to a totally different land and manage to stick around long enough to learn the language?? Please help me!! I can't stop thinking about this!!
This question (and ones like it) has been asked many times on /r/Askhistorians. Here are just some results that I found:
For the Classical world, here are two answers from /u/toldinstone and /u/mythoplokos.
Here we have /u/Tiako who quotes St. Augustine's discussing learning foreign languages.
Here is a post by /u/BRIStoneman where they discuss what a person living in Anglo-Saxon England would use to learn a foreign language.
In this answer /u/CoeurdeLionne discusses learning foreign languages in Britain during the early Norman period.
In this answer /u/WelfonaShelf discusses learning foreign languages in Muslim Spain and the Holy Land.
And if you'd like to learn more about non-European forms of education, /u/keyilan discusses Korean methods of learning foreign languages here.
Obviously there's plenty more to be said about the topic, but hopefully this is a good primer for what others have posted before.