Internet English (which includes the English peculiar to text messaging devices and apps) is a language unto itself.
If you're too young to remember the pre-Internet world, you might not realize that as recently as 1995 or 1985, no one would have made much sense over abbreviations like idk, lmk, IMO, or the venerable ROTFLMAO.
We use abbreviations because—not to put too fine a point on it—we’re too lazy to type all those words. Online communications, moreover, have an ephemeral quality. When you’re typing a text message, you’re typing something that may become completely irrelevant in less than a minute, after all.
But the preference for an economy of words is nothing new. As Tore Janson explains in his book, A Natural History of Latin (Oxford University Press, 2004), our medieval forebears were just as eager to conserve effort when writing.
For roughly a thousand years, the Church had a virtual monopoly on long-form written texts in Europe. Monks labored away in writing rooms called scriptoria, where they copied important books and documents onto pieces of parchment. Since Latin was the language of scholarship in those days, everything was transcribed in Latin, even if the monks were working in England or Ireland.
That was tedious work, as you can imagine. (Though one also imagines that it was more pleasant than being a peasant laboring in the fields.) The monks relied extensively on abbreviations. The Latin uerbum (word) might become uerbū, to cite Janson’s example.
These abbreviations followed few standards, so it is often difficult for contemporary Latinists to figure out exactly what the monks were getting at. Sometimes the meaning of an abbreviation can be reasonably inferred from context, but sometimes it comes down to sheer guesswork.
Kind of like your teenage daughter’s text communications…