"approval, endorsement," early 15c., from Old French aprobacion "approval" (Modern French approbation) and directly from Latin approbationem (nominative approbatio) "an approval," noun of action from past-participle stem of approbare "to assent to" as good, from ad "to" (see ad-) + probare "to try, test something (to find if it is good)," from probus "honest, genuine" (see prove). Also in Middle English in a now-obsolete sense of "proven effectiveness, excellence" (late 14c.).