n.1 an extra profit or allowance additional to a main income etc.
2 a customary extra right or privilege.
3 an incidental benefit attached to employment etc.
4 a thing which has served its primary use and to which a subordinate or servant has a customary right.
Etymology: ME f. med.L perquisitum f. L perquirere search diligently for (as PER-, quaerere seek)