Heel strike to the thigh ?

Hi! Recently, I've been sparring with my coach, and he caught me a few times with a strike I hadn't seen before. He hit the outside of my thigh, right on the nerve, using his heel . He didn't use much effort or force, but it was still strong enough to leave a bruise. I found it very effective, but he couldn't tell me the name of the strike. Does anyone here know what it's called? I'd love to look up some videos on it.