1765, "authenticated official report concerning some event, issued for the information of the public," from French bulletin (16c.), modeled on Italian bulletino, diminutive of bulletta "document, voting slip," itself a diminutive of Latin bulla "round object" (see bull (n.2)) with equivalent of Old French -elet (see -let). For use of balls in voting, see ballot (n.).
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). Broadcast news sense of "any brief, notice or public announcement of news" is from 1925. Bulletin board "public board on which news and notices are posted" is from 1831; computer sense is from 1979.