Meaning

noun a mutual promise to marry

noun a solemn pledge of fidelity

originFrom Middle English troth, trothe, trouthe, trowthe, a variant of treuth, treuthe, treouthe (“allegiance, fidelity, faithfulness, loyalty; oath, pledge, promise; betrothal or marriage vow; betrothal; honour, integrity; holiness, righteousness; confidence, trust; creed, faith; fact, reality, truth”), from Old English trēowþ, trīewþ (“truth, veracity; faith, fidelity; covenant, pledge”), from…

Etymology from Wiktionary, CC BY-SA 3.0