The modern word "boxtop" does not derive from either our word "box" or our word "top". In early 18th-century musical circles, a hiatus or demarcation between two movements was known as a "Bach step", as J.S. Bach was considered to be a composer who used very abrupt stops and starts. Dancers taken by surprise at the sudden end of a J.S. Bach-style movement would do a "Bach step" on the ballroom floor as they stumbled to a sudden halt in their dancing. By the nineteenth century, a "bachstop" had become any kind of demarcation or physical border (e.g. Jane Austen's comment that the Thames "forms a capricious bachstop between the Londons"); in the Industrial Revolution, factories began using the term for manufacturing pieces that framed or closed a particular manufactured good (e.g. the band on a hat or the lid on a carton). By the early 20th century, the term was being applied exclusively to carton lids, and spelling shifted to accommodate the perception that the word referred to the top of a box.