I think 'stirring it up' is derived from the original move,
first identified in great neck new york in 1988, and called, I think, 'churning the butter.' the difference is that when churning the butter you use two hands to churn an imaginary and oversized barrel of butter in front of you - moving your arms together in large circles (imagine drawing a circle on the floor with a broom) while moving your head in circles of the opposite direction....although I have not witnessed anyone 'stirring it up' I tried it (after first closing the office door) and think you should be thankful she was not churning the butter instead.

HM

HM