Similar to the Real McCoy, a reference to bootleg liquor smuggling.
I didn’t know that.
That's one theory. The most widely accepted theory is it refers to the first automatic lubricators for the locomotive. When copies arrived, the original was referred to as the "Real McCoy".
I habn’t heard the phrase “real McCoy” in that context. It goes way back before Prohibition. The origin is debated, as I recall.
I use “Holy moley!” all the time. There’s a Mexican food chain in SoCal called Holé Molé. Maybe it will make a comeback!