Arguably this is the 'cheapest' SLR lens ever available in the market with performance. And hence the nickname, again arguably the only lens to have one!
BTW, Nifty Fifty refers to those 50 legendary stocks in the New York stock exchange that were considered solid to buy and keep.
Back to the lens , this is a fixed focus 50mm lens, means no way to zoom other the you moving forward or backward with the camera to zoom. A great lens for the portrait range shots.
Its one of the fastest lenses (f/1.8) with razor thin depth of focus in the image. Its hard to get rid of this, once it find its way into your lens inventory!