1530s, "subject to (ecclesiastical) dispensation, excusable, pardonable," from Medieval Latin dispensabilis, from Latin dispensare "disburse, administer, distribute (by weight)" (see dispense).
Meaning "that can be done without" is from 1640s; that of "capable of being administered" is from 1670s. Later senses in some cases might be directly from dispense. Related: Dispensability.
