The crossword solution for the term NAPA PREFIX is OENO, which is a four-letter prefix derived from the Greek word oinos, meaning 'WINE'. It is commonly used in the naming of various WINE-related terms, such as oenology (the study of WINE and winemaking) and oenophile (a person who enjoys WINE). The prefix is also used in the name of the Napa Valley AVA, an American Viticultural Area located in California's Napa County.