Interestingly, an illegal block from behind used to be called clipping, but I haven’t heard that term used in years. Since the refs now announce the penalties over a mic, perhaps the terminology had to be dumbed down.
Actually clipping is a foul still. Clipping is an illegal block below the waist from behind. That rule changes around 15 years ago when the thought was a 15 yard fouls for a block above the waist was excessive. Agra ago, ineligible receiver down field was a five yard penalty AND loss of down. Thank God they got rid of that nasty little enforcement