"BS" is a vulgar term meaning "nonsense" or "to fake something." Unlike the Shim-Sham Shimmy, another treasured piece of tap history, the BS Chorus requires more advanced technique. It's extremely challenging if done correctly. When it became popular in the 1920s and '30s, inexperienced dancers would try to fake their way through it—hence, "BS."
“Although we don't know exactly who decided what steps to incorporate or the order in which they were originally performed, Margaret Morrison, a tap historian, performer, and co-director of tap teaching training at the American Tap Dance Foundation in NYC, believes the first two steps of the BS Chorus date back to the 1800s, when they were part of a style known as buck-and-wing—a predecessor of tap dance, which wasn't formally known as tap until the 1920s. The sequence was later popularized and presented often by The Copasetics, an ensemble of well-known hoofers formed in 1949.”
As with the Shim-Sham Shimmy, there's no one correct way to execute the BS Chorus. Most variations occur on the break, a section of most traditional routines where the dancer can inject his or her own personal flair.
No matter how you do it, the BS Chorus is an important dance to learn and keep alive: It's informed so much of tap dance and enriched how and what we teach. "We need to return the favor by doing it well and allowing it to teach us,"