The 'unintelligible' chant in the opening title song is actually intentional backmasking saying "nigerarenai" (meaning You Can't Run Away).
The nickname Rena uses when referring to Shion (Mion's twin sister) is Shi-chan. Shi means Death in Japanese. Whether this was intentional or not is up to the viewers.
The restaurant that Shion works for is called Angel-Mort. In French Mort means dead or death, depending on how you use it. Therefore, it could be read as dead angel.
The fictional village of Hinamizawa is based on the real-life village of Shirakawa, in Gifu Prefecture, Japan which is also a UNESCO World Heritage Site.
Based on a popular doujin (fan created) sound novel game. The "game" features no real interaction and the player reads through a good amount of text. There were 8 chapters to the story, each released at the Winter and Summer Comic Markets. The games were divided into two series; Higurashi no Naku Koro Ni, and Higurashi no Naku Koro Ni Kai. The former contained the first four chapters (labeled question chapters) and the latter contained the last four chapter (answer chapters). As each new game was released into the series, the former chapters were included. Buyers can now purchase the entire series on two different discs, one for the question chapters and one for the answer chapters.