The expression blouson noir designates, in French contexts, a young person, especially a young man, belonging to a youth subculture of the 1950s and 1960s, characterised by the wearing of black leather jackets, denim jeans and plaid shirts, listening to rock-and-roll music, riding motorcycles or mopeds, and popularly associated with involvement in crime and antisocial behaviour.—Hence, more generally, the expression blouson noir designates a young hooligan.

This expression occurs, for example, in Streets ahead, by Alexander Fury, published in The Independent (London, England) of Tuesday 22^nd March 2016:

Back in July 1960, Yves Saint Laurent ¹ presented his autumn/winter haute couture collection for the house of Christian Dior ². It was a collection he called “Beat”, an almost all-black parade of clothes inspired by existentialists and teen-agers hanging out on the Left Bank of Paris. It caused a scandal, particularly when Saint Laurent presented his version of a black leather jacket, seen as the garb of hooligans more likely to mug an haute couture client than be one. The term itself, “blouson noir”, was a synonym for said ne’er-do-wells. Sure, Saint Laurent’s blouson noir was in crocodile lined with mink, but it still acted as a catalyst for his departure from the house after barely three years.

¹ Yves Saint Laurent (1936-2008) was a French couturier.
² Christian Dior (1905-1957) was a French couturier.

Borrowed from French, the expression blouson noir is from the noun blouson ³, denoting a short jacket, and the adjective noir, meaning black.

³ The French noun blouson is a diminutive of the noun blouse, denoting a loose garment for the upper body.—Cf. also the informal British phrase big girl’s blouse, denoting a man regarded as weak, cowardly or oversensitive.
French formations in -on are usually diminutive.—Cf. for example the French noun chaton, kitten, diminutive of the noun chat, cat.

The earliest occurrences of the French expression blouson noir that I have found are as follows, in chronological order:

1-: From the following article, published in Combat (Paris, France) of Friday 24^th July 1959:

Les « blousons noirs » de Vanves et de Plaisance devaient attaquer ceux de Saint-Lambert
[…]
Animés par l’esprit de « Graine de violence » ⁴, une centaine de galopins s’étaient « mobilisés » la nuit dernière pour une guerre des rues qui, dans le 15^e arrondissement, a été évitée de justesse grâce à l’intervention des gardiens de la paix.
L’affaire avait débuté dans le quartier du square Saint-Lambert où se réunissent quelque cinquante garnements habitués à jouer les « gros bras » devant les filles du quartier.
Or, les « gars » de Saint-Lambert étaient en effervescence : ils avaient appris que leurs rivaux de Vanves et de Plaisance, des « blousons noirs » comme eux, devaient descendre à leur rencontre pour leur faire la guerre.
     translation:
The “blousons noirs” of Vanves and Plaisance were to attack those of Saint-Lambert
[…]
Driven on by the “Blackboard Jungle” ⁴ spirit, about a hundred youths had “mobilised” last night for a street war which, in the 15^th arrondissement, was only just avoided thanks to the policemen’s intervention.
The matter had started in the area of the Saint-Lambert public gardens where get together some fifty tearaways accustomed to play the tough guys in front of the local girls.
Now, the “lads” of Saint-Lambert were in a turmoil: they had learnt that their rivals of Vanves and Plaisance, “blousons noirs” like themselves, were to come down and meet them to wage war on them.

⁴ Graine de violence [i.e., Violence in the making] is the French title given to Blackboard Jungle (1955), a U.S. cinema film directed by Richard Brooks (1912-1992), starring Glenn Ford (1916-2006) and Sidney Poitier (1927-2022), adapted from Blackboard Jungle (1954), a novel by the U.S. author Evan Hunter (1926-2005).

2-: From Amélioration ou décadence de l’espèce humaine ?, by Hilaire Cuny, published in Combat (Paris, France) of Wednesday 29^th July 1959:

L’« affaire des blousons noirs » a mis en transes nombre de nos contemporains que la jeunesse appelle, avec autant d’humour que d’irrespect, les « croulants », dont je fais partie.
     translation:
The “blousons noirs affair” has put in agony a number of our contemporaries whom the youth call, with as much humour as disrespect, the “crumblies”, of whom I am one.

3-: From the column Au pied levé [i.e., At a moment’s notice], by ‘Le Crabe’, published in Cols bleus. Journal de la Marine française (Paris, France) of Saturday 1^st August 1959:

Londres a ses « teddy-boys », Varsovie ses « houligans », New York, Chicago, Stockholm et toutes les grandes villes du monde leurs bandes de jeunes voyous aux dénominations locales diverses mais aux activités similaires.
Paris a ses « tricheurs », ses « blousons noirs » et ses « chemises rouges ».
     translation:
London has its “teddy-boys”, Warsaw its “hooligans”, New York, Chicago, Stockholm and all the big cities in the world their gangs of yobs with various local denominations but with similar activities.
Paris has its “tricksters”, its “blousons noirs” and its “red shirts”.

4-: From the title of an article published in Combat (Paris, France) of Wednesday 5^th August 1959:

Les blousons noirs
(suite)
La « Bande de la croix de pierre » sème la terreur dans un bal rouennais
     translation:
The blousons noirs
(continued)
The “Bande de la croix de pierre” spread terror at a ball in Rouen

In the following, published in Combat (Paris, France) of Wednesday 5^th August 1959, Pierre-Bernard Marquet wrote that the social phenomenon referred to by the expression blouson noir was already attracting media attention:

Jeunesse en blousons
L’« information générale » est pleine, depuis quelques jours, des « exploits » des bandes de jeunes gens en blousons noir ou marron.
     translation:
Youth in blousons
“General news” has been full, for several days, of the “exploits” of the bands of youths in black or brown blousons.

The earliest occurrences of the expression blouson noir that I have found in texts in English are as follows, in chronological order:

1-: From the News Chronicle and Daily Dispatch (London, England) of Friday 7^th August 1959:

Teddy gang beats up holiday camp
From John Tomiche

PARIS, Thursday.—A forty-strong gang of teenagers using nail-studded sticks and bicycle chains as weapons raided a holiday camp near Toulon, on the Mediterranean coast, late last night.
Five teachers, two women and three men were injured, but police arrived in time to round up 15 youths, all aged between 14 and 17.
This is the fourth outburst of violence in a fortnight by organised youth gangs. The incidents have deeply shocked public opinion.
The French Teddy boys are called either tricheurs (tricksters) or blousons noirs (black windcheaters—which are part of their uniform).
A recent survey estimated that there were some 50 gangs in Paris, each a hundred strong. Every gang rules and operates in its own territory.

2-: From The Daily Telegraph and Morning Post (London, England) of Monday 17^th August 1959:

FRENCH TEDDY BOYS BECOME GANGSTERS
CAMPERS ATTACKED
FROM OUR OWN CORRESPONDENT

PARIS, Sunday.
ACTIVITIES of gangs of French Teddy boys are causing increasing concern in France. Although they have been known to exist for some time, they have not until the past few weeks been much more than nuisances.
But recently they have developed into juvenile gangsters and earned themselves the nation-wide title of Blousons Noirs because of the black garments they wear. They have injured a number of people in attacks on persons and property.
Their habits do not differ much from those of young hooligans of other countries. They arm themselves with knives, bicycle chains, clubs and buckled belts. On a number of occasions recently they have attacked holiday campers.
Some of the bands have been as many as 30 strong and of ages ranging from 10 to 20. A recent fracas in Paris brought a comment from the chief of police that he was not going to stand that sort of thing in the capital.
CLASH WITH POLICE
On the Mediterranean coast, there has been more than a little evidence of the strength of these gangs. They clashed with police near Toulon after damaging a casino and since then a number have been arrested. They recently created trouble in the centre of Nice by an attack on an open-air ball.
From elsewhere in the country have come reports of serious damage to schools and other buildings, of robberies and of occasional injuries resulting from clashes between rival gangs. There is little the authorities can do except issue warnings and impose punishment on those found guilty.
But police throughout France intend to crush this social menace as soon as possible. A documentary film with the title “Les Blousons Noirs” is being made in Paris.

3-: From The Miami News (Miami, Florida, USA) of Sunday 23^rd August 1959:

Mon Ami, Eet’s Bad To Be Bored…
N. Y. News—Miami News Service

PARIS, Aug. 22—Police today announced 170 “blousons noirs” (black jackets) were rounded up yesterday and last night in a crackdown on young hoodlums.
Police said 15 of the youths—aged mostly between 13 and 26—were kept in custody and will be charged with inflicting wounds.
About 10 passersby on Dancy Street were injured last night when the black-jacketed youths attacked persons “whose face we do not like”—one tough told police afterward.
Asked why they acted this way, one of the youths said:
“When the day’s work is over, one gets bored.”

4-: From The Guardian (Manchester, Lancashire, England) of Monday 24^th August 1959:

Crowding in Paris

The French police are taking stern measures against the gangs of “blousons noirs,” or Teddy-boys, who have been beating up passers-by (“because we don’t like their faces”) in Paris suburbs and near Toulon. Until now France has been fairly free of the teen-age hooliganism which has troubled the rest of Europe, not even stopping at the Iron Curtain. But its turn was bound to come, and there are, indeed, special causes for delinquency there. Chief among these is the housing situation which, in spite of considerable efforts on the part of the Government during the past year, remains incredibly difficult. A recent survey in a French newspaper showed that in a district of Paris there were scores of families living in one or two rooms each, with the children sleeping in the same bed as their parents or brothers and sisters. In the same district there were two small open spaces—quite insufficient for the thousands of children who have no other playground than the streets. And this situation, which is at its most acute in Paris, is reproduced in most large French cities. In 1952 an inquiry showed that even in twelve country departments one family in three was living in one room. Even when dwellings are constructed, they are likely to be archaic in character (in 1951 half of them were without bathrooms). The reasons are twofold. First, the idiotic policy of rent restriction pursued by the Third Republic which meant that by about 1930 it had become uneconomic to build at all or even to repair existing buildings. Secondly, the archaic state of the French building industry (200,000 firms employing an average of three workers each), which was described by a Minister of Reconstruction as living in the age of the Merovingians. Things may be a little better now than immediately after the war, but French adolescents still find it impossible to stay at home, and still have nowhere to go but the streets. “Les toits de Paris” are picturesque to look at, but less so to live under.

The following interesting remarks are from The Observer profile of Brigitte Bardot ⁵, published in The Observer (London, England) of Sunday 27^th September 1959:

A number of solemn attempts have been made to isolate her sociological significance. One American critic described her as “the symbol of the loneliness and insecurity of modern youth.” In a recent analysis of the Bardot myth, Simone de Beauvoir ⁶, the novelist, compares her with James Dean ⁷ and detects the same dominant traits: “the fever of living, the passion for the absolute, the sense of the imminence of death.”
In some respects she does represent the blouson-noir teddy-boy type of problem child, who gratuitously flouts conventional standards without replacing them with any coherent new philosophy. Family, politics, religion and thought are excluded from the myth. Instinct and self-satisfaction are the driving force.

⁵ The French film-actress Brigitte Bardot (born 1934) rose to fame in the late 1950s.—Cf. the French noun bardotlâtrie.
⁶ Simone de Beauvoir (1908-1986) was a French philosopher, playwright and novelist.—Cf. the phrase the second sex, denoting women collectively, regarded as inferior to men.
⁷ James Dean (1931-1955) was a U.S. film-actor.