What is "chiltern hundreds"

Chiltern Hundreds \Chiltern Hundreds\ [AS. Chiltern the Chiltern, high hills in Buckinghamshire, perh. Fr. ceald cold + ern, [ae]rn, place.] A tract of crown land in Buckinghamshire and Oxfordshire, England, to which is attached the nominal office of steward. As members of Parliament cannot resign, when they wish to go out they accept this stewardship, which legally vacates their seats. [1913 Webster] ||

The Chiltern Hundreds was an ancient administrative area in Buckinghamshire, England, composed of three " hundreds" and lying partially within the Chiltern Hills. "Taking the Chiltern Hundreds" now refers to the legal procedure used to effect resignation from the British House of Commons. This is because the ancient office of Crown Steward for the area (in full Crown Steward and Bailiff of the three Chiltern Hundreds of Stoke, Desborough and Burnham), having been reduced to a mere sinecure by the 17th century, became the first to be used in this resignation procedure a century later. Other titles were also later used for the same purpose, but at present only the Chiltern Hundreds office and the Crown Steward and Bailiff of the Manor of Northstead are used.