I found this in a word site, that seems reaonably authentic:
"Promulgate is derived from the Latin promulgatus, the past participle of promulgare, a conjunction of pro- (forward) and mulgare (probably akin to mulgare which meant to milk, extract). This word has been in English use since the early 1500s."

So much for "caprimulgidae" except I wonder what the basis for the "goat sucking" was. Some birds in that family do have a very big mouth. I saw an injured one, with insect catchin
bristles around its mouth, which could have accomadated a sow's teat.