Gorp wasn't even a word until 1968. It's an acronym for "good old raisins and peanuts," a snack mix of high-energy food.   It has become a more common trail food than peanut butter on a Triscuit, and it's way handier.   In its simplest form, gorp is raisins and peanuts fancied up with M&Ms, dried fruit, seeds and just about any food that's small, firm, tasty and naturally grown.   Inventive campers will add cereal, dried peppers, chocolate chunks, pretzels, even Goldfish crackers to the mix.   In a rush? Supermarkets carry bags of the stuff in the snack section.

Colin Fletcher, one of America's most celebrated writers in the backpacking field and author of "The Man Who Walked Through Time" (Vintage, $13) and "River" (Vintage, $16) admits gorp has become his basic snack.  "The term embraces a wide spectrum of mingle-mangles, usually based on dried fruit and nuts, sometimes with chocolate or carob," Fletcher wrote in "The Complete Walker IV" (Knopf, $22.95).   His favorite is a commercial concoction called Tropical Trail Mix (date pieces, raisins, sunflower seeds, coconut chips, pineapple pieces, banana chips, papaya, almonds and peanuts).   Of course, you can always select and mix your own ingredients.

Sue Roberts, a registered dietitian from Des Moines, Iowa likes to keep things simple.   These are her preferences:

-Nuts: "A variety of nuts is great," she says. They make the gorp filling and provide both protein and fats (which are good fats and OK if eaten in small amounts). She chooses raw, unsalted ones, but any are fine if one must have the roasted and salted ones.

-Roasted soy nuts: Great for the phytoestrogens. These come in many flavors; Roberts prefers the plain, salted variety.

-Dried fruit: A must in a gorp mixture for both flavor and nutrition. Roberts likes all dried fruits and uses a mixture. "I always include craisins (dried cranberries) for a healthy urinary tract, dried blueberries to help my brain and dried cherries," she says.

-Seeds: Add a few roasted pumpkin seeds or sunflower seeds.

Then there's chocolate: "If someone has to have this, like many of us do, go with a really good dark chocolate (more antioxidants)," Roberts says. "I use some really good dark chocolate chips or pieces of dark chocolate bars with fruit. They are delicious."

She recommends staying away from M&Ms in the mix -- "lots of not-too-good things in those," she says.

Horace Kephart, a Jefferson, Iowa native who was considered the dean of American camping in the early 1900s, recognized long ago the importance of chocolate in his book, "Camping and Woodcraft" (University of Tennessee, $16.95).

"Chocolate never gets stale," Kephart wrote. "It requires no cooking, can be eaten on the march ... It is the experience of Alpinists and other go-light artists that no other raw food of equal weight and bulk will carry a man so far under severe strain as a handful of raisins and a cake of chocolate."

Today, caffeine-free carob that tastes a bit like chocolate, though not nearly enough for some, is substituted in some gorp blends.   Other gorp fans, who aren't so picky about nutritional detail, find M&Ms to be a cheap and practical choice for a cocoa kick.