Core vocabulary is that part of a language that changes least through time and space.
This is crucial in determining the history of a language itself and the related history of the culture of which it’s a part. In the absence of historical documents or archeological evidence, frequently the case with tribal cultures, it’s better than nothing. It’s also necessary in reconstructing the proto-language for what is now a family of related languages. For the traveler it goes beyond the usual pronouns, basic foods, small numbers, and body parts, into such abstract categories as fast food, intimate clothing, large numbers, and body parts. Fortunately the term ‘blow job’ forms part of the International Scientific Vocabulary, so readily understandable anywhere, at least in certain circles. This is the DNA of culture, the penis-tracks of history, the linguistic trails that linger long after the original encounter with imminent change. You create a new world when you look into your lover’s eyes.