Probity, n.
Etymology: [F. probité, fr. L. probitas, fr. probus good, proper, honest. Cf. Prove.]
Tried virtue or integrity; approved moral excellence; honesty; rectitude; uprightness. "Probity of mind." Pope.
Syn. -- Probity, Integrity. Probity denotes unimpeachable honesty and virtue, shown especially by the performance of those obligations, called imperfect, which the laws of the state do not reach, and can not enforce. Integrity denotes a whole-hearted honesty, and especially that which excludes all injustice that might favor one's self. It has a peculiar reference to uprightness in mutual dealings, transfer of property, and the execution of trusts for others.
Shades of meaning
Fernald has no entry of its own for probity; he lists it under virtue.
Where he writes about it:
Honesty and probity are used especially of one's relations to his fellow men, probity being to honesty much what virtue in some respects is to goodness; probity is honesty tried and proved, especially in those things that are beyond the reach of legal requirement; above the commercial sense, honesty may be applied to the highest truthfulness of the soul to and with itself and its Maker. — from virtue