The derivation
πείθω is the word for persuasion — but its etymology argues that persuasion is the late meaning, and trust the old one. Both surviving authorities (Frisk treats the family s.v. πείθομαι, but that article is missing from our source parse) head the verb not at the active πείθω "I persuade" but at the middle πείθομαι "I trust, rely, obey, am persuaded," and both judge the active to be derivative. Chantraine states it directly: "L'actif transitif est p.-ê. secondaire" — the transitive active is perhaps secondary (Chantraine, DELG s.v. πείθομαι). The primary thing is not to win someone over but to be won over: to place one's confidence.
The root is *bʰeidʰ- "to convince, trust," and its cognate is the keystone of the entry. Beekes lines them up: Latin fīdō "to trust," fidēs "trust, guarantee," foedus "treaty, agreement" — alongside Albanian besë "faith" and Old Church Slavonic běda "distress, necessity" with běditi "to force, persuade" (Beekes, EDG s.v. πείθομαι). The Greek persuasion-word and the Latin word for good faith are the same word. And Chantraine, leaning on Benveniste, makes the priority explicit: "Les mots de cette famille expriment originellement la notion de «confiance, fidélité»… avec diverses implications juridiques" — the family originally expresses confidence, fidelity, with juridical force, "ce sens est apparent dans les termes les plus archaïques" — visible in the most archaic terms, πιστός "faithful" and πίστις "faith, pledge" — "Les formes groupées sous B. au sens de «persuader» sont secondaires" — the persuasion-forms are secondary (Chantraine, DELG s.v. πείθομαι, Et.).
The disagreement the entry foregrounds is not between dictionaries but inside the word: trust versus compulsion. The same *bʰeidʰ- that yields fidēs yields Gothic baidjan "to force," and OCS běditi "to force, persuade." Benveniste's resolution, which Chantraine quotes, is that the Germanic beidan "to wait" means first "to wait with confidence, to put one's trust in," and baidjan names "une contrainte morale qui n'est que de persuasion" — a moral constraint that is only persuasion (Chantraine, DELG s.v. πείθομαι, Et.). So the root holds trust, persuasion, and force in one grip: to be persuaded is to be brought, willingly or under moral pressure, to entrust yourself.
Root
- *bʰeidʰ- "to convince, trust" — Beekes and Chantraine (Frisk absent from the parse). Cognates: Latin fīdō "trust," fidēs "trust, guarantee," foedus "treaty"; Albanian besë "faith"; OCS běda "distress" / běditi "to force, persuade"; Gothic beidan "to wait," baidjan "to force."
- Order of senses (Benveniste, via Chantraine): the original sense is trust / fidelity, with juridical weight (πιστός < *bʰidʰ-to-, πίστις an action-noun); persuasion (the active πείθω, the Πειθώ-forms) is a secondary Greek development. Pokorny 117.
In the corpus
1,927 occurrences in the corpus — one of the largest soul-words, and its sheer spread mirrors the semantic range the etymology predicts: from trusting and obeying to persuading by, in Chantraine's catalogue, "le raisonnement, les prières, la force, l'argent" — reasoning, prayers, force, money. The family's most consequential offshoot is πίστις, "faith, trust, pledge" — the action-noun that Chantraine glosses "comme lat. fidés" and that the New Testament would make its central word for faith; beside it πιστός "faithful," πιθανός "persuasive, plausible," and the personified Πειθώ, goddess of Persuasion (Hesiod). One Homeric hapax fixes the quiet end of the range: at Odyssey 20.23, ἐν πείσῃ κραδίη μένε — the καρδία, the heart, "stayed in confidence," steady and trusting under provocation.
The word's world
πείθω names persuasion as a power that binds. For Marcel Detienne, Peitho is not a rhetorical technique but one of the sacred forces of "magico-religious speech," standing with Dike (Justice) and Pistis (Trust) in the archaic configuration of efficacious utterance (Detienne, The Masters of Truth in Archaic Greece). Michael Naas, reading the Iliad under the heading "Persuasion, Confidence, Trust," draws the same circle the etymology draws: "Related to confidence in oaths and covenants is confidence in oneself, one's abilities, one's friends, and the signs given by the gods" — persuasion is continuous with the trust that swears oaths and the trust one places in one's own θυμός (Naas, Turning: From Persuasion to Philosophy). The word's history and its world converge on a single claim: to be persuaded is to extend faith, and the Greek for I trust and the Latin for good faith were never two words.
Authorities: Beekes, Etymological Dictionary of Greek (Brill 2010) s.v. πείθομαι (scan pp. 1212–1213, #4864); Chantraine, Dictionnaire étymologique de la langue grecque s.v. πείθομαι (scan pp. 885–886, #6348; Et. section under #6349, scan p. 886). Frisk, Griechisches etymologisches Wörterbuch: treats the family s.v. πείθομαι (per the cross-reference stub at πίστις, scan p. 1516, #4665), but the article is absent from the source parse and is not quoted. Root *bʰeidʰ- and the trust-before-persuasion ordering per Beekes / Chantraine, after Benveniste, Institutions indo-européennes 1.115–121; Pokorny 117. Interpretive sources retrieved from the Oracle library (Classical Philology & Ancient Thought): Detienne, The Masters of Truth in Archaic Greece (1996); Naas, Turning: From Persuasion to Philosophy (1995). Corpus figures: Logoi corpus, live. Receipt: soul-word-journey-v0.