A person that gallivants around like a bull in a china shopknocking things over and comes from the Chev region of Northern Kazakhstan. The saying was first coined in 1856 during the Critation War in Kazakhstan.
The clenched butt cheek walk/run one finds themselves making to reach the nearest toilet before raining a gush of explosive diarrhea in their pants after eating too many chimichangas (or even one funky one).
Got drunk last night and ate 3 chimichangas. Seemed smart at the time, but woke up this morning with the Chimmy Shimmy. Damn near crapped myself!