hello:
1883, alt. of hallo (1840), itself an alt. of holla, hollo, a shout to attract attention, first recorded 1588. Perhaps from holla! "stop, cease." Popularity as a greeting coincides with use of the telephone, where it won out over Alexander Graham Bell's suggestion, ahoy. Central telephone exchange operators were known as hello-girls (1889).
"Hello, formerly an Americanism, is now nearly as common as hullo in Britain (Say who you are; do not just say 'hello' is the warning given in our telephone directories) and the Englishman cannot be expected to give up the right to say hello if he likes it better than his native hullo. [H.W. Fowler, "A Dictionary of Modern English Usage," 1926]
http://www.etymonline.com/index.php?term=hello
Alteration of hallo, alteration of obsolete holla, stop!, perhaps from Old French hola : ho, ho! + la, there (from Latin illāc, that way).
Hello is a salutation or greeting in the English language and is synonymous with other greetings such as Hi or Hey. Hello was recorded in dictionaries in 1883.
Many stories date the first use of hello (with that spelling) to around the time of the invention of the telephone in 1876. It was however used in print in Roughing It by Mark Twain in 1872 (written between 1870 and 1871), so its first use must have predated the telephone:
"A miner came out and said: 'Hello!'"
http://en.wikipedia.org/wiki/Hello
