“The word lox has become synonymous with smoked salmon, but that’s not how it started out,” says Niki Russ Federman, co-owner of Russ & Daughters in Manhattan. “The original lox is what my great-grandpa sold off his pushcart 100 years ago. It’s called belly lox; it’s a salt-cured belly portion of the salmon.” Belly lox is very strong and salty, and Federman says that the classic lox, bagels, and cream cheese combo came about because the salt-cured lox was so intense that you needed the dairy to cut it. At Russ & Daughters, it’s made by packing sides of salmon (preferably king salmon because it can stand up to the salt without disintegrating) in dry salt for about a week, then transferring the sides to a wet brine with about 60 percent salinity, where the fish cures for around six months.
“[The term] lox is used generically,” says Ira Goller, the owner of Murray’s Sturgeon Shop in Manhattan. “We have to ask customers if they mean salty or smoked salmon.”
Gravlax, on the other hand, is a specific term that refers to the traditional Scandinavian preparation of cured salmon. Goller says that it’s unsmoked, and traditionally made with a smaller, less fatty salmon, which has sugar, salt, spices, and dill packed around it. The fish is then weighed down and placed in the refrigerator for two to four days to cure. It’s pretty easy to make yourself if you have good-quality salmon to work with: Chowhounds have lots of tips and our Cured Salmon recipe from Chef Traci Des Jardins is close to a traditional gravlax.
Many languages have a word similar to lox that means salmon. According to Merriam-Webster’s online dictionary, the English use of it stems from the Yiddish word laks, which arose from the Middle High German word for salmon, lahs. Federman says gravlax gets its name from the old-school preparation: burying the fish in a salty grave (grav) in the ground.