1530s, from Latin aequabilitatem (nominative aequabilitas) "equality, uniformity, evenness," figuratively "impartiality," from aequabilis "equal, consistent, uniform" (see equable).
Entries linking to equability
equable adj.
1670s, back-formation from equability or else from Latin aequabilis "equal, consistent, uniform, not varying" from aequare "make uniform" (see equate). Related: Equably; equableness.