Meaning

noun any of various long-tailed rodents similar to but larger than a mouse

noun someone who works (or provides workers) during a strike

noun a person who is deemed to be despicable or contemptible

originFrom Middle English raat, rat, ratt, ratte, rotte, from Old English ræt, rætt, from Proto-West Germanic *ratt, from Proto-Germanic *rattaz, *rattō (“rat”), of uncertain origin, possibly from Proto-Indo-European *Hreh₃d- (“to gnaw, scrape, scratch”). However, the rat may have been unknown in Northern Europe in antiquity, and the Proto-Germanic word may have referred to a different animal; see…

Etymology from Wiktionary, CC BY-SA 3.0