Hello

The word hello, a greeting between persons when meeting, is from the 1840s in the frontier of the western US. At that time, the terms “Hello” or “Hello, the house” were the usual greetings upon approaching a home.
 
Hello is a version of hallo or holla, a shout first seen in the late 14th century as a way to attract attention. There are at least a dozen forms of ‘hello’ that have appeared over the years (e.g., halloo, hillo, holler, holloa, hullo, and many others).
 
When the telephone was patented in 1876, the question arose, “What do you say when you answer the phone?” Alexander Graham Bell’s suggestion was, “Ahoy!” Thomas Edison is said to have preferred, “Hello”. Other early telephone greetings included, “Do I get you?” and “Are you there?”
 
Needless to say, “Hello” has become the way in which telephones are generally answered. In the 1880s and 90s, the telephone exchange operators were known as ‘hello girls’.
 
Another variation of hello is “Hail” as in “Hall to your grace” or “Hail Caesar.” The word hail is related to words such as hale, health, and whole.
 
Reference: Online Etymological Dictionary, https://www.etymonline.com/
https://www.merriam-webster.com/dictionary/hello