When combined, 礼拜 (lǐbài) means “to worship” or a “religious service,” specifically the weekly Christian one. The system of naming days of the week using “礼拜” + a number was introduced by Christian missionaries. Therefore, 礼拜五 is literally the “fifth day of the worship week.”
The existence of three common words for the days of the week (星期, 周, and 礼拜) tells a small story about modern Chinese history. The term “礼拜五” is a direct cultural import, a remnant of Western missionaries introducing the seven-day week concept tied to their Sunday (礼拜天) worship. In comparison to American/Western culture, this is similar to how “Thursday” is named after the Norse god Thor. While the origin is religious or mythological, the modern usage is entirely secular. No one in China thinks of Christian worship when they say “礼拜五”; they think, “Thank goodness the weekend is almost here!” The feeling of “礼拜五” in China is identical to “Friday” in the West. It represents the end of the demanding work or school week, a time for relief, and the beginning of social activities, relaxation, and family time. The universal “TGIF” (Thank God It's Friday) feeling is just as palpable in Beijing or Shanghai as it is in New York or London.
“礼拜五” is extremely common in daily conversation across China, though it is sometimes considered slightly more prevalent in southern China and Taiwan.