early 15c., "rejected as worthless," from Late Latin reprobatus, past participle of reprobare "disapprove, reject, condemn," from Latin re- "back, again," here perhaps indicating "opposite of, reversal of previous condition" (see re-) + probare "prove to be worthy" (see probate (n.)). The meaning "abandoned in character, morally depraved, unprincipled" is by 1650s.
1540s, "one rejected by God, person given over to sin," from reprobate (adj.). Sense of "abandoned or unprincipled person" is from 1590s.
early 15c., reprobaten, "condemn, disapprove vehemently," from Late Latin reprobatus, past participle of reprobare "disapprove, reject, condemn" (see reprobate (adj.)). Later coming to mean "reject, put away, set aside" (by c. 1600). Related: Reprobated; reprobating.