Possible origin: Whippersnapper

One of the easiest skills learned by an inexperienced cowboy is that of snapping a black snake whip. Those who couldn’t bulldog a steer or rope a maverick prided themselves on being able to strut into a town while calling attention to themselves by snapping their whips. Only youngsters who didn’t even carry guns followed this practice. But it was common enough to lead people who never worked a trail herd to adopt whippersnapper as the perfect label for any brash, but unskilled, beginner.

And yes, about the only people who still use the phrase are just us “old foggies.” Lol

Here is some interesting history on the word. It comes from our early west.

Just about anyone who is called a “whippersnapper” is either a juvenile or a learner who is barely dry behind the ears. One of the easiest skills learned by greenhorn cowboys is that of snapping a black snake whip, or bullwhip. Long ago, lots of young fellows who could not bulldog a steer or rope a maverick prided themselves on being able to strut into town while calling attention to themselves by snapping their whips. Older townsfolk were quick to adopt “whippersnapper” as just the right label for any brash but unskilled beginner.