"characteristic of or suitable for Christmas," 1852, from Christmas + -y (2).
Entries linking to christmassy
Christmas n.
"Church festival observed annually in memory of the birth of Christ," late Old English Cristes mæsse, from Christ (and retaining the original vowel sound) + mass (n.2).
Written as one word from mid-14c. As a verb, "to celebrate Christmas," from 1590s. Father Christmas is attested in a carol attributed to Richard Smart, Rector of Plymtree (Devon) from 1435-77. Christmas-tree in the modern sense is attested by 1835 in American English, rendering German Weihnachtsbaum. Christmas cards were first designed in 1843, popular by 1860s; the phrase Christmas-card was in use by 1850. Christmas present is from 1769. Christmas Eve is Middle English Cristenmesse Even (c. 1300).
-y 2
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy). Adjectives such as hugy, vasty are artificial words that exist for the sake of poetical metrics.