Those new to fly fishing often complain of an aching hands/fingers, or worse still tennis elbow (tendentious) when first picking up a fly rod. It can also affect the most experienced of anglers on a bad day.
A slight variation on this is the “screwdriver grip”, which again is holding the rod as though you where gripping a screwdriver, so the’V’ between thumb and index finger is now situated on top of the rod handle.