In Appalachia: A History, John Alexander Williams says this about the term Appalachia:
As if the varying boundaries weren't enough, there is no fundamental agreement even about how to pronounce the word "Appalachia." Residents of southern and central Appalachia pronounce the term with a short -a- in the stressed third syllable; further north, the same -a- is given a long pronunciation, as in "Appal-achia." Most of the experts and bureaucrats who came from Washington and elsewhere to fix the region's problems beginning in the 1960s adopted the northern pronunciation, while resident experts favor the southern-- which led to a situation, according to one commentator, wherein "people who said AppaLAYchia were perceived as outsiders who didn't know what they were talking about but were more than willing to tell people from the mountains what to do and how they should do it." Finally, while a majority of both long and short -a- users crunch the third syllable as though it were spelled Appal-atch-yuh, in New England-- where the term "Appalachian" first came into widespread use by nongeologists thanks to the Appalachian Mountain Club and the development of the Appalachian Trail-- a variant pronunciation uses "sh" rather than "ch," as in Appal-ay-shuh.