[Daub]

One advantage of using hello as a greeting is that it is agnostic of social rank. This made it the perfect choice for greeting people of unknown social rank on the phone.

Having traveled the world quite a bit I can attest to the ubiquity of the word hello… almost everywhere I go it is understood. ‘OK’ has a similar ubiquity, and it is interesting that both words are relatively new additions to the English (universal?) language.

[bloppe]

These are called translingual words. 2 interesting ones are coffee and chocolate. basically no matter where you are in the world, people will understand those (with slight regional differences like "cafe", similar to hello)

[pezezin]

Chocolate is native to the Americas and started to spread around the world in the 17th century, so it makes sense that most languages use the same word, as it is a quite recent addition.