Wy does the default "omw" keyboard shortcut keep putting itself back on my iPhone??

That's one of the first things I did, delete that shortcut because it totally defeats the purpose, "omw" is 3 only characters long and everyone knows what it means. Especially when texting to a non iOS person, when the number of characters counts, so this is a ridiculous shortcut to have, in my opinion. I delete it, but then eventually it just comes back which is really annoying! How do I erase that shortcut and KEEP it gone??