Closing Bell can refer to two CNBC programs, the original Closing Bell on CNBC, and European Closing Bell on CNBC Europe.
The show is named after the bell that is rung to signify the end of a trading session on the New York Stock Exchange which occurs at 4:00 pm EST. Many exchanges used to signify end of trading with a gong or bell when they were operated on a open outcry basis. The New York Stock Exchange still uses this system and often invites special guests to ring the bell.
The CNBC shows use this name as they cover the period up to the end of trading and review the trading of the day after the market has closed.