The Spanish word 'equidad' (meaning 'equity' or 'fairness') comes from the Latin word 'aequitas', which meant 'equality' or 'fairness'. 'Aequitas' itself was formed by combining the Latin root 'aequus' (meaning 'equal') with the suffix '-itas' (which was used to form abstract nouns indicating a quality or state).

Several common Spanish words share the same Latin root 'aequus', including: 'igual' (equal), 'ecuación' (equation), and 'equilibrio' (equilibrium). All these words carry the core meaning of equality or balance from their shared ancestor.

Many English words are related to 'equidad' through the same Latin root 'aequus', including 'equal', 'equity', 'equation', and 'equitable'. The English word 'equity' is particularly close in both meaning and form to the Spanish 'equidad', as both descended from Latin 'aequitas'. In English, like in Spanish, these words maintain the fundamental concept of fairness and equality from their Latin origin.