Why is the ninth month called September?
1765, from French bulletin (16c.), modeled on Italian bulletino, diminutive of bulletta "document, voting slip," itself a diminutive of Latin bulla (see bull (n.2)). The word was used earlier in English in the Italian form (mid-17c.). Popularized by their use in the Napoleonic Wars as the name for dispatches sent from the front and meant for the home public (which led to the proverbial expression as false as a bulletin). Bulletin board is from 1831.