Holy crap, Rilchiam, you’re right. I was thinking of Serena Joy from The Handmaid’s Tale by Margaret Atwood. Don’t know what made me conflate those two.
I’ve always used “safeword” as a safe word.
Always have. Always will.
No confusion, and it’s a big pain to try to sort through your brain for an obscure (or at least non-obvious) safe word while someone is cutting or piercing you.