turd, crap, fecal matter
“Il se fait foutre et fouetter alternativement par deux hommes, pendant qu'il encule un jeune garçon et qu'un vieux lui fait dans sa bouche un étron qu'il mange.” — He got fucked and whipped in turn by two men, while he buggered a young boy and an old man did a turd in his mouth, which he ate.
Inherited from Middle French étront, from Old French estront, from Late Latin struntus, borrowed from Frankish *strunt, from Proto-Germanic *strunt- (“stump”), from *strent- (“to be stiff”), from Proto-Indo-European *(s)ter- (“stiff”). Compare Italian stronzo (“asshole, dumbass”), Dutch stront (“feces, turd”), West Frisian stront, English strunt (“tail”), Middle High German strunze (“stump”), Luxembourgish strëllchen, dialectal Swedish strunt (“a bud, sprout, offshoot”).