The type of abbreviations that have been in common usage for many years didn't exist at all until people started to use them. The ones used on Gransnet didn't either, but they have been used here for the past ten years, to my own certain knowledge, and I believe they were used on social media before that.
There are a lot of complete words in common use today that were unknown if you go back fifty years - or even twenty, for some. Email is one. Texting is another. Same with foods. Would you have known what a tamarillo was, or couscous, or the difference between a chicken korma and a chicken Madras, before you saw them in a supermarket or on a menu?
When you first went onto the internet, you picked up the words for what you were doing there. When you started going to Indian restaurants, you picked up the names of things on the menu. Now that you are posting on social media, you are meeting common abbreviations. If you use them, you will pick up (or guess) what they are abbreviatons of. If you avoid them you will never know.