In the United Kingdom, Ireland and some Commonwealth nations, knickers is a word for women's undergarments. George Cruikshank, whose illustrations are classic icons for Charles Dickens' works, also did the illustrations for Washington Irving's droll History of New York (published in 1809) when it was published in London. He showed the old-time Knickerbockers, Irving's fictitious Dutch colonial family, in their loose knee-length Dutch breeches. Consequently, by 1859 relatively short loose ladies' undergarments, a kind of abbreviated version of pantalettes or pantaloons, were known as "knickers" in England.
In Australian and British usage the term is often used in the expressions "Don't get your knickers in a twist" and "Don't get your knickers in a knot". In U.S. usage, its equivalent is "don't get your panties in a bunch."
Note that while the term 'knickers' refers almost exclusively to women's underwear, 'knicks', knick-knacks' and similar more masculine variations are acceptable monikers for men's underwear, particularly for young boys.
In India, the term is not used exclusively for women's shorts - boys' or men's shorts are also referred to as 'knickers'.