Autocorrect on iPhone and iPad is an essential feature for most of us. The idea is that Autocorrect learns as you use your devices, learning new words from you and making changes based on what it thinks you would say. But sometimes it goes awry: you typed a made-up word once and now it wants to use that word all. the. time. Unfortunately, iOS and iPadOS do not let you customize your personal dictionary manually. If you want to get rid of something you have to wipe out the whole list of custom words. Which may not be terrible.
To do that go to the Settings app > General > Transfer or Reset iPhone (or iPad) > Reset > Reset Keyboard Dictionary. The exact names of these menus might be different in older versions, but this is where you will find it in iOS 15 and iPadOS 15.