One of the mysteries of the English language finally explained.
Definition of perequation in US English:
perequation
noun
rareThe action of making equal; specifically the addition of an amount to one price or cost to make it equal to another. Also occasionally: a state of equality or fairness.
Origin
Early 17th century; earliest use found in Randle Cotgrave (fl. 1587–?1630), lexicographer. From French péréquation from classical Latin peraequātiōn-, peraequātiō state of being equal from peraequāt-, past participial stem of peraequāre to make equal (from per- + aequāre) + -iō.