We've Had Black Monday, Black Tuesday, and Black Friday... What Would Cause a Future "Black Wednesday" or "Black Thursday"?

I've been reading about some of the biggest market crashes in history: ​ Black Friday (1869) – Gold market collapse. Black Monday (1929) – Major crash during the start of the Great Depression. Black Tuesday (1929) – Continued panic selling that accelerated the collapse. Black Monday (1987) – The largest one-day percentage drop in U.S. stock market history. ​ It got me thinking: ​ What kind of event would be required for the market to earn a new name like "Black Wednesday" or "Black Thursday" in the future?