When the word promulgate ("to make widely known") was first brought into the English language in 1526, it was spelled promulgat, and it stayed that way until the e was standardized in the late seventeenth century. It comes from Latin promulgatus, which was the past participle of the verb promulgare, with the same definition. Beyond this, there are two theories. There's definitely the prefix pro-, meaning "forth", but the root could be either an alteration of vulgare, which translates to "to publish", or mulgere, which meant "to milk" (or, more metaphorically, "to bring forth"). Personally, I like the second explanation better because it doesn't make much sense to me that an m would just change to a v unless it was conflated with another word. Mulgere is from Proto-Indo-European melg, "to wipe off".
Hello! I'm Adam Aleksic, a senior studying government and linguistics at Harvard University, where I co-founded the Harvard Undergraduate Linguistics Society. In addition to etymology, I also really enjoy trivia, politics, vexillology, geography, board games, conlanging, art history, and law.