You’re right: quietus (and its opposite, inquietus) appears several times in the Latin. And, yes, it’s where our modern word “quiet” comes from, although in Latin it means something a little different: from quiesco: “I rest, sleep, repose” and also “I cause to cease, stop, render quiet.” You’ll remember that Hamlet’s To Be Or Not To Be monologue has him wondering whether he himself should his Quietus make/With a bare Bodkin. But the WW connection to the Essay on Epitaphs is an excellent link: thanks! I will explore further.