What is the X in X-mas?
1520s, "act of entering," from Middle French entrance, from entrer (see enter). Sense of "door, gate" first recorded in English 1530s.
"to throw into a trance," 1590s, from en- (1) "put in" + trance (n.). Meaning "to delight" also is 1590s. Related: Entranced; entrancing.