According to the Oxford English Dictionary, hello is an alteration of hallo, hollo, which came from Old High German "hal, hol, emphatic imperative of haln, holn to fetch, used especially in hailing a ferryman." It also connects the development of hello to the influence of an earlier form, holla, whose origin is in the French hol (roughly, 'whoa there!', from French l 'there'). As in addition to hello, hallo and hollo, hullo and (rarely) hillo also exist as variants or related words, the word can be spelt using any of all five vowels.

Hello, with that spelling, was used in publications as early as 1833. These include an 1833 American book called The Sketches and Eccentricities of Col. David Crockett, of West Tennessee
Hello is alternatively thought to come from the word hallo (1840) via hollo (also holla, holloa, halloo, halloa). The definition of hollo is to shout or an exclamation originally shouted in a hunt when the quarry was spotted:
According to the American Heritage Dictionary, hallo is a modification of the obsolete holla (stop!), perhaps from Old French hola (ho, ho! + la, there, from Latin illac, that way).[17] Hallo is also used by many famous authors like Enid Blyton. Example:"Hallo!", chorused the 600 children.

The Old English verb, hlan ( to heal, cure, save; greet, salute; gehl! Hosanna!), may be the ultimate origin of the word.[18] Hlan is likely a cognate of German Heil and other similar words of Germanic origin. Bill Bryson asserts in his book Mother Tongue that "hello" comes from Old Englis ...more

I think just like in hindi as "hilo" then speak. do not be calm.

Source: self