"Swearing" is exactly the right word.

Melissa Mohr, in Holy Sh#t: A Brief History of Swearing is perfectly titled. She emphasizes that bad language use in Western society, specifically English, pendulums between profanity and obscenity, the holy and the shit. We are in an obscenity phase now, as in Roman culture. The Middle Ages was a time of swearing great religious-based oaths casually. The way we say "Fuck that" they said "Damn it to hell."

This changed in the later 1800s. Mohr cites one only court case in the US supporting a pre-ACW date, but I believe this is an outlier. A missionary to the courts and prisons of London particularly notes that after 1880 he began to hear both lowlifes and middle class miscreants switch from thoughtless "awful" oaths to filthy obscenities when talking casually or testifying. So I would consider the latter date for when the switch became common, not unusual.

Part of the reason is the failure of belief in the magic of these oaths. The more secular society became, the less emotive power it had to curse something or to swear by holy objects. The classic "gadzooks" was worn down from "By God's hooks" which might refer to hands or the nails of the Crucifiction. One late Ren French king (sorry, away from my books) swore "Par bleu!" (By blue!) to step down from "Par Dieu!" (By God!) which most of the court used. He also took to fining them for the heavier oath. So the medieval French were in the same place, using oaths rather than obscenities.

So the nobles are definitely swearing, while the peasantry is damning stubborn pigs like they had souls and emphasizing statements about housekeeping by swearing on God's blood or various saints.