I have an iPhone and noticed that it changed actual real words, to other words, even when you originally spelt the word you wanted to use correct, it'll still change the odd word for you to something it thinks you were meant to type. Over time, it learns what you type a lot of, and will give preference to those words over others.
Here's some iPhone AutoCorrection text messages gone wrong.....
View attachment iPhone-AutoCorrect.pdf
Here's some iPhone AutoCorrection text messages gone wrong.....
View attachment iPhone-AutoCorrect.pdf