I replicated something similar a few years ago using a bent trowel and pulling it away with a rocking motion. I don't think that's how it was done originally but the results was indistingushable.Idk what it's called. Crowfoot or stomp (as celicaxx said) sounds about as good as anything. It's all over the ceilings in my house. It's ugly and an PITA if you have to fuss with ceilings.
It's basically just a thin layer of mud spread on and then dabbed with ... well, I'm sure there are different kinds of specific tools, but just about anything. Dab on, pull off.