Sleeping bag : noun (word coming from leg). The wriggling is the act of moving the legs vigorously, and, by extension: agitation of the limbs, of the whole body.
And by extension, to be agitated, to get angry.
Quote from the French writer Louis-Ferdinand Destouches dit Céline (1894-1961) “Any social system delivered to the magnificent instincts of the people (Humanity dixit), system of any formula, the most ingenious, the most meticulous, the more astute, the best balanced, can end after eight days, fifteen days of attempt only with sadistic squabbles, in circuses of beheaded, in infernal antics. " in Trivia for a massacre - 1938.