The Celtic people are descended from the original inhabitants of the British Isles, before the invasions of the Romans, Angles, Saxons, Danes, and Romans. Their unique cultures remain today in Ireland, Scotland, and Wales, along with a host of smaller localities like Cornwall and the Isle of Man.
Celtic immigrants and their descendants have contributed greatly to the development of the United States of America. The first surge of immigration took place in the first half of the eighteenth century when thousands of Catholics fled the Hanoverian regime that ruled England and identified Protestantism with social acceptability. Others fled economic hardship for a land of opportunity. Those identified as Scots-Irish soon became prominent on the frontier, particularly in the Southeast. The first American President from this line of immigration was Andrew Jackson.
During the 1840`s, Irish immigration surged as a result of the Great Potato Famine in Ireland. These Celtic immigrants were not generally welcomed, representing both the Catholic religion that few native-born American at the time shared, and a low level of education of culture. The gradual emancipation of the Irish in America culminated in the election of 1960 when John F. Kennedy won the presidency.
The epitome of the "canny Scot" was probably Andrew Carnegie, who emigrated from Scotland in 1847 with no money and rose to be one of the country`s richest men through his control of a vast empire of steelmaking. His legacy was spread across through the country with the innumerable Carnegie Public Libraries in small towns, as well as Carnegie Hall in New York City.
The pronunciation of the word is invariable with a hard "c" as in "Keltic," with one exception. The NBA basketball team from Boston is spelled "Celtic" and pronounced "Selltick." Maybe it comes from "selling tickets."