Origins: Derived from the term Chicken McNally, which itself was derived from Chicken McNugget. McNally is a more general term than Chicken McNally, used to describe some snackable food morsel that is not necessarily made out of chicken.
A person who is prone to doing something or going somewhere without having any idea of what they are getting into
We went for McNally hike the other day, got totally lost and had a few near death experiences
Anyone else: "Dood, I got those like a month ago you fucking Johnny"
McNally: "What's up?"
Revis: "Shutup McBitch!"