"Primavera" had been used in English before 1976 to describe other Italian dishes, such as "Chicken alla Primavera" and "risotto primavera."
Wikipedia: Pasta primavera
Pasta primavera is an Italian-American dish that consists of pasta and fresh vegetables. A meat such as chicken, sausage or shrimp is sometimes added, but the focus of primavera is the vegetables themselves. The dish may contain almost any kind of vegetable, but cooks tend to stick to firm, crisp vegetables, such as broccoli, carrots, peas, onions and green bell peppers, with tomatoes. Pasta primavera is usually highlighted by light flavors, aromatic herbs and bright colors ('primavera' meaning the season of spring). Classic pasta primavera is based on a soffritto of garlic, olive oil, and Parmesan cheese, but versions based on a heavier cream or Alfredo sauce are also common. Though recipes for cold pasta primavera may be found, they are best classified as antipasti, or appetizers.
Pastas served with this dish are typically smaller shapes, such as penne, farfalle, rigatoni and fusilli. If using longer types of pasta, such as spaghetti or fettuccine, the vegetables are normally sliced in thin strips to match the shape of the noodles.
Since primavera means spring, the vegetable choices should be the crisp new vegetables of spring.
Though this dish is related to and likely derived from genuinely Italian dishes, under this name it is certainly an American dish, created in New York City in the early 1970s. The canonical story of its creation ascribes it to Sirio Maccioni, then owner of Le Cirque, in 1974. Soon it gained popularity as an unlisted special at the restaurant, and from there spread rapidly across the country.
8 October 1972, Lowell (MA) Sun (FAMILY WEEKLY):
Wandering down a narrow street, we savor the aroma of simmering Minestrone, laden with ring-shaped pasta and tiny meatballs. It is a radiant afternoon, and our appetites quicken at the sight of Roast Chicken alla Primavera, wreathed with spaghetti, rich red sauce and fresh garden vegetables.
23 June 1974, Washington (DC) Post, pg. L16:
The restaurant's (Harry's Bar--ed.) specialties are a pasta known as taglatelle, risotto primavera and scampi and it serves the best hamburgers outside the United States.
19 July 1976, New York magazine, "Party Fare" by Gael Greene, pg. 44, col. 3:
Haut pasta: The best spaghetti in town is spaghetti primavera at Le Cirque, 58 East 65th Street, 794-9292, where the lunch-munchers are so spectacularly skinny and chic and beautiful that most of us have never heard of them.
24 September 1976, New York (NY) Times, Restaurants by Mimi Sheraton, pg. 65:
The spaghetti primavera at Le Cirque, 58 East 65th Street, is a far happier memory. Served as an appetizer or a main course, the medium-fine spaghetti is tossed with bright green al dente flowerets of broccoli, slivers of zucchini and snow peas, slices of mushrooms, sauteed cherry tomatoes and toasted pignoli nuts all with gentle hints of garlic, parsley and fresh basil -- an extraordinary dish, and a classic.
31 January 1977, New York magazine, "I love Le Cirque, but can I be trusted?" by Gael Greene, pg. 62:
Still, when it is brilliant, you are dazzled. Todeschini's spaghetti primavera is as crisp and beautiful as a Matisse. I have called it the best pasta in town.
...and that spectacular spaghetti primavera. Would life be worth living without pasta? Especially this pasta -- tart tomato red, garden green of broccoli and pea, a shadow of mushroom, pine nuts, torn leaves of basil, some butter, and a splash of cream.
(Le Cirque, 58 East 65th Street -- ed.)
26 August 1977, New York (NY) Times, Le Cirque review (one star) by Mimi Sheraton, pg. 58:
Spaghetti primavera, not on the menu, but one of the best house specials--which can be had as an appetizer of a main course--is another dish that varies. One night the spaghetti, though slightly undersalted, came with a satiny rich sauce of consomme, cream and cheese that bound bits of vegetables such as zucchini, mushrooms, flowerets of broccoli, pease, string beans and lightly sauteed diced tomatoes together, all with a few pignoli nuts included for a bit of crunch.
2 October 1977, New York (NY) Times, "Spaghetti With A French Accent," by Craig Claiborne and Pierre Franey, pg SM20:
By far the most talked-about dish in Manhattan today is a creation of Italian origin that flourishes in one of the most popular of the city's luxury French restaurants, Le Cirque, at 59 East 65th Street. It is an inspired blend of pasta and crisp, tender vegetables, such as zucchini and mushrooms and broccoli and green beans, plus cheese, cream and toasted pine nuts. These are tossed hot and crowned with a delicate fresh tomato sauce. Although the dish is called spaghetti primavera--spaghettis with a springtime air--it is served all year long at Le Cirque. It can be reproduced easily in the home.
The dish, as served in the restaurant, is the collaboration of Jean Vergnes, the French owner-chef, and Sirio Maccioni, his elegant Italian co-owner and major-domo of the dining room.
20 March 1991, New York (NY) Times, "What Makes Food Italian? Don't Ask American Chefs" by Florence Fabricant, pg. C1-pg. C6:
Of the numerous pasta dishes that are served with vegetables in Italy, none are called primavera (springtime). "I invented the dish in 1974," said Sirio Maccioni, the owner of Le Cirque in New York. "It seemed like a good idea and people still like it."
New York (NY) Times
Le Cirque’s Spaghetti Primavera
By AMANDA HESSER
Published: May 14, 2009
But in the late 1970s, when New York’s Le Cirque popularized spaghetti primavera, Craig Claiborne and Pierre Franey called it “by far, the most talked-about dish in Manhattan.” At least three people laid claim to its creation. According to David Kamp, in his excellent book, “The United States of Arugula,” spaghetti primavera was the brainchild of either Ed Giobbi, an artist and cook, who prepared it for Sirio Maccioni, the owner of Le Cirque, and Jean Vergnes, the chef at Le Cirque; or Maccioni’s wife, as Maccioni wrote in his memoirs; or Vergnes, who doctored Giobbi’s version with cream and vegetables. Despite his assertion that he invented it, Vergnes was said to have hated the dish so much, he forced his cooks to make it in a hallway.