in dancing, "a rapid whirling on one leg or on the points of the toes," 1706, from French pirouette "spinning top; pirouette in dancing," from Middle French pirouet "spinning top" (15c.), from Gallo-Roman root *pir- "peg, plug" (source of Italian piruolo "peg top") + diminutive suffix -ette. Hence, probably, U.S. Civil War slang piroot "to move or travel listlessly or aimlessly" (1863).
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