sacking out
n.— «One of the main tools to getting the horse used to human touch is a technique called sacking-out. “It comes from an old term where they used to take a gunny-sack and rub it all over the horse,” he said. “It desensitizes them to being touched. It spooks them a bit at first, but then they realize your not trying to hurt them and they accept it.” McCone brought out a long wooden stick with a coarse woven plastic bag on the end of it. He gently laid the sack on the horse’s back, moving it around. The horse was tense at first, but as Charlie spoke to the horse it started to relax and soon paid no attention to the sack.» —“A passion for horses” by Eric Posz Redwood Falls Gazette (Minn.) May 3, 2005. (source: Double-Tongued Dictionary)