A Meritage is a blend of grapes in the Bordeaux style - Cabernet Sauvignon, Merlot, Cabernet Franc, Petite Verdot and Malbec for the reds and Semillon, Sauvignon Blanc, and Sauvignon Vert for the whites. The organization was created in 1988 and you have to pay to use this on your wine label and become a member of the organization.
Unfortunately, the mispronunciation is propagated throughout the wine world daily, even by wine professionals and in wine shops. Let's start getting it right in Durham and spread the word in proper English outward! -Salamanzar