There are various ways in which culture spreads from one place to another. There are missionaries who use religion to spread their influence. There is the military which subdues other groups with might and conquest.
And perhaps, the most convenient of them all and least menacing, the merchants who trade wares and goods as they travel to various places. Along with the products they sell, these merchants also bring with them words which are unique to their own culture. Through their interactions with other merchants, they get to share their language and exchange ideas.
The map shown above illustrates only a few of the words that have been taken from their native languages and how they were adapted by other languages.
(Image credit: Lapham's Quarterly)