Equity is a roguish thing. For Law we have a measure, know what to trust to; Equity is according to the conscience of him that is Chancellor, and as that is larger or narrower, so is Equity. ’T is all one as if they should make the standard for the measure we call a “foot” a Chancellor’s foot; what an uncertain measure would this be! One Chancellor has a long foot, another a short foot, a third an indifferent foot. ’T is the same thing in the Chancellor’s conscience.Grammar.com's section on Problem Words discusses equable and equitable. Click here for that discussion.
—John Selden Table Talk. Equity.