I think the dichotomy of venial versus mortal over a specific thing like this is not helpful.
The important thing is whether you are in a state of grace. It’s something you can know if your heart. If you love God with all your heart, soul and mind there is a good chance you can experience what it feels like to be pure of heart. The indwelling Holy Spirit will flee long before you say the “f-word” and you may actually be able to pin-point in a thought you have or decision you make long before you take any concrete physical action. Like a light switch going off. This is what Jesus is talking about in the sermon on the mount. It is not about rules but about loving God through Jesus in the Holy Spirit. I would urge you to not focus on venial versus mortal but focus on your relationship with God through Jesus in the Holy Spirit. The f-word isn’t going to help your purity of heart, that’s for sure.
If you are still trying to make the acronym case, no. That is an urban legend. There is 0 evidence for it.Read any etymological treatment of the f word. No.
DISCLAIMER: Catholic Answers has turned over the archive to Catholic-Questions.org and no longer owns, manages, or moderates the forums. For additional apologetics resources please visit www.catholic.com.