What is the X in X-mas?
mid-13c., morn, morewen (see morn) + suffix -ing, on pattern of evening. Originally the time just before sunrise. As an adjective from 1530s. Morning after in reference to a hangover is from 1884; in reference to a type of contraception, attested from 1867. Morning sickness as a symptom of pregnancy is from 1793 (Old English had morgenwlætung). Morning glory is from 1814, in reference to the time the flowers open. Morning star "Venus in the east before sunrise" is from 1530s (Old English had morgensteorra "morn-star"). As a greeting, short for good morning, attested by 1895.