Dr., Mrs., Ms. etc. are traditionally abbreviated with periods/dots but it does raise issues typing on one’s phone because autocorrect thinks it’s the end of a sentence, so sans dots is becoming more common. And there’s other examples which have never had dots, like nvm and af
X is a little special, it stands for Cross and therefore also for Christ. When illiterate medieval people had to sign documents they were told to make the sign of the Cross, since they were usually swearing
Edit: anyone else always pronounce PED XING as pedexing instead of pedestrian crossing?