Replying to Kink Rails

Can someone explain to me why a double kink is called a quad kink in skiing? I come from a rollerblading background and we always refer to a single kink (down flat down) as simply kink rail. Double kink (down flat down flat down). Triple kink (down flat down flat down flat down). For the most part anytime theres a kink in the rail (flat section) you count that as one. I constantly see captions for tricks that say quad kink rail when its a double kink. I realize we all have different names for tricks... Just wondering!?