What is OPETH and how do I get it?

Currently I am trying to use velodrome finance on optimism and when I want to convert my velo from V1 to V2 I need to pay the fee in OPETH. I have OP in my Wallet but when I want to sign IT says "Insufficient funds". I was thinking its a pair from a Pool but I have never seen that you need to pay fees with a pair.

So what exactly is OPETH and whats the easiest way to get some small amount so I can pay fees?