the.com/pillbox hat

means A small, brimless hat with straight sides and a flat top, shaped like a cylindrical box, traditionally worn perched forward on the head.

from Named simply for its resemblance to the small cylindrical boxes once used to dispense pills — flat-topped, straight-sided, lidded containers that pharmacists and travelers carried. The hat style itself has military roots, echoing the stiff cylindrical caps worn in various 19th-century uniforms, before it crossed into civilian fashion and became a staple of mid-20th-century women's millinery, famously associated with Jacqueline Kennedy's understated, elegant styling.