The modern word salad goes back to the Latin salata, “salted.” A popular dish in ancient Rome was herba salata, salted vegetables.
Although salata‘s root is sal (salt), salad eventually came to refer to the leaves alone, and the seasoning for it assumed the name (salad) dressing. Many food writers say that salad dressing is a sauce… which seems perfectly fine, but still I want to know why it wasn’t called salad sauce. My theory is that the word dressing is applied to salad in the sense of finishing, decorating, serving… something to that effect.
Salad dressings have come a long way from the time of the Romans, whose go-to seasoning for raw leaves was brine (water-salt solutions). They eventually began to serve their mixed greens with separate containers for vinegar and oil, a practice that continues to this day. I like to tell friends (in serious jest) that they must not think of Caesar Salad as a standard order when they tour Italy; neither must they ask for bottled “Italian dressing” even if that’s their favorite.
There are many stories about the origin of Caesar Salad. I will state here the most popular account, that the dish was invented in a Tijuana (Mexico) restaurant, close to the San Diego border. Chef Caesar Cardini is said to have put it together for straggling patrons one late night, using the few ingredients left in his kitchen. It was a nameless concoction for a while, but word-of-mouth about its appeal made it a frequent order. Instead of having people describe what they want by enumerating the ingredients (hand-torn Romaine lettuce, olive oil, lemon juice, coddled egg, grated Parmesan cheese, etc.), he lent his name to the new customer favorite: Caesar Salad!
As noted above, stories abound on the salad’s origin. Do your own internet search and be ready to encounter assorted versions. For me, the overarching consideration is that the lettuce-dressing combination was thus put together, and now the recipe is there for us to enjoy… whatever its permutations.
As to Italian dressing, do note that it is an American invention. Its main ingredients are vinegar or lemon juice and vegetable oil: the two components of generic salad dressing in Italy. Bottled Italian dressing contains additions such as chopped bell peppers, herbs and spices such as oregano, fennel, and dill, seasonings such as salt and a sweetener, and more.
Bottled Italian dressing also sees general use as a marinade. Sometimes it doubles as dip for blanched vegetables, or as a sprinkle on certain sandwich fillings. The uses are limited only by your imagination!
Some Italian dressings get more spice treatment, and are labeled as Zesty Italian. With the addition of buttermilk, it gets to be called Creamy Italian.