equanimous means impartiality, equality, constancy. It is that which has or demonstrates tranquility, moderation, serenity, justice, or is the one who always has the same spirit, who is aware of what he does or what he says. from latin aequanimus (here - equal, anime - mood).
Equanimity is an adjective of two genders, which refers to what has or in which there is equanimity, that is, that has equality of courage in the face of adversity or prosperity, good or bad circumstances, which has serenity of mind and fairness in to judge.
Equity is the willingness to equally recognize each one's right. It is the set of immutable principles of justice that lead a judge to a criterion of moderation and equality, even at the expense of objective law; it is the feeling of justice that opposes a criterion of judgment or a rigorous and strictly legalistic treatment.
To give equal treatment to all judgments is to exercise a natural justice, which makes everyone's right to be impartially recognized, with equality and moderation.