betroth

the word "betroth" is a verb formed from the combination of the intensive prefix "be-" and the noun "troth," an old english word for truth or fidelity. "troth" itself derives from the old english "trēowth," meaning faithfulness, which is related to "true." thus, the literal action of "betrothing" is to pledge one's truth or faithfulness to another. this formal promise of marriage historically functioned as a binding contract, emphasizing the solemn duty and truthfulness inherent in the engagement. the term preserves the archaic noun "troth," which survives in modern english primarily within this compound and the phrase "plight one's troth."

Structure: be + troth be- (prefix of Germanic origin, meaning "about, around, thoroughly"); troth (noun from Old English, meaning "truth, faithfulness, pledge")