The name "Nevada" comes from the Spanish adjective "nevada", meaning "snow-covered" or "snowy". The state takes its name from the Nevada Territory, which in turn was named for the Sierra Nevada. Nevadans pronounce the second syllable with the "a" of "apple" while some people from outside of the state pronounce it with the "a" of "palm". Although the quality, but not the length, of the latter pronunciation, is closer to the Spanish pronunciation, it is not the pronunciation used by Nevadans.

Source: Wikipedia