There was a wealthy Italian who was building a villa in the US, and told the architect he wanted a "hollow statue" in it. The architect looked far and wide for a hollow statue, without success. Finally he came back to the client and told him that no one he talked to had heard of hollow statues. The client said, "Oh, it's one of those things that rings, and you pick it up and say "Halo, 'stat you kiddo?"

And likewise became EHLO which could also be used as a greeting over the phone if you were you were talking to an email server.