Why do they call a dressing a Vinaigrette ?

[ibcheft]

Why is it they call a dressing for salad a Vinaigrette, when there is no vinegar in it ? as say in this summer salad posted in another post
Watermelon and Cantaloupe Salad with Mint and Basil Vinaigrette

1/2 watermelon
1 cantaloupe, cut in half, seeded
2 tablespoons freshly chopped mint leaves plus whole sprigs, for garnish
2 tablespoons freshly chopped basil leaves plus whole sprigs, for garnish
1 lemon juiced (1/4 cup)
1/4 cup simple syrup (equal amounts sugar and water heated until sugar dissolves, cool)
1/8 teaspoon amaretto

Recipes : Watermelon and Cantaloupe Salad with Mint and Basil Vinaigrette : Food Network

is this a French thing, something in the classic cooking education ?

[Food Network Fan]

A vinaigrette is formulaic, its basic components usually 3 parts oil (olive, walnut, etc.) to 1 part acid (red wine vinegar, lemon juice, etc.), a little mustard to help the oil and vinegar mix, plus salt and pepper. Tasting helps you adjust the ratio each time. Vinaigrettes are potent sources of taste and flavor. Oil, acid and salt stimulate three of five tastes the tongue detects: bitter (oil), sour (acid) and salty (salt). Diced relatives of the onion add sweetness and pungency. (When I have time, I let diced shallot or onion mellow in the acid for 15 minutes before adding the oil, a la Alice Waters’ suggestion in her book Chez Panisse Vegetables.) A touch of soy sauce, miso, ketchup or diced tomato can complete the taste spectrum by bringing umami and additional sweetness. Chopped herbs add lots of flavor.
I usually default to olive oil, champagne vinegar and lemon juice. But the beauty of thinking of vinaigrettes as a combination of set components is that it allows you the freedom to mix and match the components according to what’s in your refrigerator and pantry, which type of cuisine you’re aiming for and what kinds of tastes and flavors you’ll be dressing.
Once you know the formula, a quick whisk and drizzle can elevate an otherwise too-plain dish. Some good matches: asparagus with a lemon tarragon vinaigrette; grilled chicken with a miso vinaigrette; roasted pork loin with a rosemary balsamic vinaigrette. Once you’re comfortable with the formula, the combinations are endless.

SOURCE

[Food Network Fan]

I guess it's any acid. In that one, seems like it would be the lemon.

[Bentley Green]

Did anyone know that vinagrette is one of the 5 mother sauces?