This wasn’t just a quirk of Burns, but a joke about his age:
Alexander Graham Bell initially suggested that the standard greeting when answering a telephone should be “ahoy”, but instead “hello” (suggested by Thomas Edison) was adopted.
I still think we should switch over to Italian answering:
“Pronto!” == ‘ready’
I understand this was/is a joke. That being said, Topsy may have a slightly differing opinion on that.
Edit: I made friends with the RBB&BC elephants before they were retired. I only interacted with them 4 times for less than a week at a time before they were retired. When I visit them in Florida, they know who I am and act like giant puppies whenever they smell me near. I have a particular love for elephants and orca.