How.About.That
Teaching a lesson earlier today, I saw “rack my brain”† for maybe the first time (as differentiated from "wrack my brain", with a W). Or, if I'd seen it before, I never noticed. So I checked some dictionaries to see if the problem lies with me or if I'd found a simple misspelling. That led me to this, which is fascinating.
† See also, “nerve-racking”.