system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did the very first sets of global traders and explorers sailing into a foreign land learn to communicate with its people?
gpt
Drinking and whoring.

There are always pubs and brothels by the ports.  Bartering items for alcohol and sex don't require words to be spoken, and both are good places for learning words, phrases, and cultural norms.  Complete immersion in a foreign culture allows you to pick up conversational fluency in a relatively short time.  Once the basics are established, learning about what goods are desired or offered in a port becomes the basis for further trade.

Soon, offices are established, and emissaries are posted to look after the shippers' interests during their absences.  They teach others, and soon there can be thriving trade between the cultures.

...or they get slaughtered as soon as they land, and no trade is ever established.  That happened as well.

But the short answer really begins and ends with boozing and whoring.