alt Hacker NewsOne 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.
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)