'knickerbockers' originates from the surname 'Knickerbocker,' which was used by Washington Irving in his book 'A History of New York' to describe Dutch settlers in New York.

'Knickerbocker' was used to describe the style of trousers worn by these settlers, eventually becoming the modern term 'knickerbockers.'

Initially, it referred to the Dutch settlers, but over time it evolved to describe a style of trousers.