Will Elder, the Mad Magazine artist who helped introduce Yiddishisms and Borscht Belt humor into the American lexicon, died May 15 at the Jewish Home in Rockleigh, New Jersey. He was 86. Born Wolf William Eisenberg in New York, Elder was part of a stable of artists who illustrated the scripts of Harvey Kurtzman, who founded Mad in 1952. His style, which he called "chicken fat" - tasty but lacking in nutrition - most closely mirrored the tangents Kurtzman enjoyed in his writing: Elder stuffed his panels with verbal and visual puns and caricatures that had little to do with the story. Kurtzman and Elder introduced Jewish humor and language into corners of the United States that otherwise would never have encountered them.