Landscapers were using them to carry 2 5-gallon landscape pots in each hand.
A company called Vargo sells something very similar they call a "Titanium Pot Lifter" but when this is resold on a major online store it becomes a "Titanium Pot Gripper"; I hesitate to provide a link since it is commercial but I'm sure you can do a search. A pot 'lifter' could be a number of things, so maybe the 'gripper' is a better label, being both descriptive and specific to the application.
The function seems to be to ease the work of moving pots, where normally the strain goes to the thumb and two or three fingertips and transfers the weight to the palm of the hand. I'm sure if you are unloading a delivery of a semi truck load of pots this tool would be one of your best friends.