Predecessor to the landing drag chute ... which pre-dated the speed brakes installed in modern jets.
Landing drag chutes were invented during WW2. Initially, LDC were used by assault gliders to steepen landing approaches.
Later in the war, Nazis used drag chutes to help early jets slow down after landing. Drag chutes work great for that role .... Er ..... shortening landing roll but are a bloody nuisance to repack and wear out pretty quickly in that high-friction and high-temperature zone behind a jet fighter.