troth
/trəʊθ/noun
mass noun
1
- archaic & formal faith or loyalty when pledged in a solemn agreement or undertaking〈古, 正式〉忠实, 忠诚：
a token of troth.
忠诚的象征。
2
- archaic truth〈古〉真实, 真理。
短语
pledge（或plight）one's troth
- make a solemn pledge of commitment or loyalty, especially in marriage（尤指婚礼中的）盟誓。
词源
Middle English: variant of TRUTH.