Recent trends are popularizing the term elsewhere in the United States. Popular entertainer, Broadway star and Hollywood actress Bette Midler, born in Honolulu, uses the greeting frequently in national appearances.
Hello (first attested in 1826), from holla, hollo (attested 1588). This variant of hallo is often credited to Thomas Edison as a coinage for telephone use, but its appearance in print predates the invention of the telephone by several decades.
Ultimately from a variant of Old English ēalā, such as hēlā, which was used colloquially at the time similarly to how hey and (in some dialects) hi are used nowadays. Thus, equivalent to a compound of hey and lo. Used when drawing attention to yourself.
Possibly influenced by Old Saxon halo!, imperative of halōn (“to call, fetch”), used in hailing a ferryman, akin to Old High German hala, hola!, imperative forms of halōn, holōn (“to fetch”). More at hallo.