The word "hello" was specifically invented for answering telephones and didn't exist in common usage before 1876. When Alexander Graham Bell created the telephone, he needed a new word for this unprecedented form of communication.
Before telephones, people greeted each other with "Good day," "How do you do," or simply tipped their hats. Bell initially suggested that telephone users should answer with "Ahoy-hoy" (which is why Mr. Burns in The Simpsons still uses this greeting—it's historically accurate).
Thomas Edison disagreed with Bell and proposed "hello" instead, arguing that it was short, clear, and easily understood through the primitive telephone technology of the time. Edison's suggestion won out, and by 1880, "hello" had become the standard telephone greeting.
The weird part? "Hello" spread from telephones back into face-to-face conversation. Before the telephone, if you wanted to get someone's attention, you'd say "Hoy!" or "Halloo!" The modern "hello" as a general greeting didn't exist until people started using telephone language in everyday conversation.
By 1900, "hello" had completely replaced older greetings in most English-speaking countries. A technology that was supposed to transmit existing language actually created new language that transformed how humans greet each other forever.
Today, over 7 billion people use a word that was invented specifically for a machine that most of us now carry in our pockets. Every time you say "hello," you're using telephone technology vocabulary.