Christianity (n.)youdaoicibaDictYouDict[Christianity 词源字典]
c. 1300, cristente, "Christians as a whole; state of being a Christian," from Old French crestienté "Christendom; spiritual authority; baptism" (Modern French chrétienté), from Church Latin christianitatem (nominative christianitas), noun of state from christianus (see Christian). Gradually respelled to conform with Latin. Christendom is the older word for it. Old English also had cristennes.[Christianity etymology, Christianity origin, 英语词源]