Question

why we say hello when we get wish someone else

Answer 1

The dictionary says it was Thomas Edison who put hello into common usage. He urged the people who used his phone to say "hello" when answering. His rival, Alexander Graham Bell, thought the better word was "ahoy."

Answer 2

We say hello because the first person in the world who had used the phone had said it to his wife .And this trend is continuing till now.