A Norfolk jacket is a loose, belted, single-breasted

Single-breasted

In clothing, single-breasted refers to a coat, jacket or similar garment having one column of buttons and a narrow overlap of fabric. In contrast, a double-breasted coat has a wider overlap and two parallel rows of buttons....

 jacket with box pleat

Pleat

A pleat is a type of fold formed by doubling fabric back upon itself and securing it in place. It is commonly used in clothing and upholstery to gather a wide piece of fabric to a narrower circumference....

s on the back and front, with a belt or half-belt. The style was long popular for boys' jackets and suits, and is still used in some (primarily military and police) uniforms. It was originally designed as a shooting coat that did not bind when the elbow was raised to fire. It was named either after the Duke of Norfolk

Duke of Norfolk

The Duke of Norfolk is the premier duke in the peerage of England, and also, as Earl of Arundel, the premier earl. The Duke of Norfolk is, moreover, the Earl Marshal and hereditary Marshal of England. The seat of the Duke of Norfolk is Arundel Castle in Sussex, although the title refers to the...

  or after the county of Norfolk

Norfolk

Norfolk is a low-lying county in the East of England. It has borders with Lincolnshire to the west, Cambridgeshire to the west and southwest and Suffolk to the south. Its northern and eastern boundaries are the North Sea coast and to the north-west the county is bordered by The Wash. The county...

 and was made fashionable after the 1860s in the sporting circle of the Prince of Wales, later Edward VII

Edward VII of the United Kingdom

Edward VII was King of the United Kingdom and the British Dominions and Emperor of India from 22 January 1901 until his death in 1910...

, whose country residence was Sandringham House

Sandringham House

Sandringham House is a country house on of land near the village of Sandringham in Norfolk, England. The house is privately owned by the British Royal Family and is located on the royal Sandringham Estate, which lies within the Norfolk Coast Area of Outstanding Natural Beauty.-History and current...

in Norfolk.