From French 'discrediter' (to strip trust) — 'dis-' + 'credit' (belief). To discredit is to undermine the grounds for belief.
To harm the good reputation of; to cause an idea or piece of evidence to seem false or unreliable; loss or lack of reputation or respect.
From French 'discréditer' (to deprive of credit, to strip of trust), from 'dis-' (depriving of, reversing, negating) + 'crédit' (credit, trust, belief), from Latin 'crēditum' (a loan, something entrusted), from 'crēdere' (to believe, to trust, to entrust), from PIE *ḱred-dheh₁- (to place one's heart, to believe — literally 'to put heart'). The PIE compound is from *ḱerd- (heart) + *dheh₁- (to put, to place): belief is the act of placing one's heart in something. Latin 'crēdere' produced 'credit,' 'credible,' 'credential,' 'creed,' 'grant' (via
The phrase 'to discredit a theory' is one of the most important operations in science. Karl Popper's philosophy of science held that scientific knowledge advances not by proving theories true but by discrediting (falsifying) theories that are false. A theory that cannot in principle be discredited — that is unfalsifiable — is, in Popper's view, not scientific. So the act of discrediting is, paradoxically, one of science's most constructive activities.