The name made me wonder as well when we visited the waterfall.
It seems the saying "it's raining cats and dogs" has another take in French: "il pleut comme vache qui pisse".
This was the base for changing the name from la cascade de Salanfe to La Pissevache. Or so the story goes
This is only the bottom part. The complete waterfall measures 116 meters.
I didn't get a good overall view though, too close.