Why does my iPhone sometimes add a (space) and a b instead of the normal . (space) when I double-tap the space bar?

I sure don't have anything like that setup in Settings > Keyboard > Text Replacements which I do use for many other words that I post often on Facebook. But it just keeps happening every now & then. I can't get it to do it intentionally even if I keep doing different things.

So, what the heck is going on?

I do know that these iPhones tend to have a mind of their own on lots of things.