What is the X in X-mas?
late 14c., from Old French tradicion (late 13c.), from Latin traditionem (nominative traditio) "delivery, surrender, a handing down," from traditus, past participle of tradere "deliver, hand over," from trans- "over" (see trans-) + dare "to give" (see date (n.1)). The word is a doublet of treason (q.v.). The notion in the modern sense of the word is of things "handed down" from generation to generation.
any kind of teaching, written or spoken, handed down from generation to generation. In Mark 7:3, 9, 13, Col. 2:8, this word refers to the arbitrary interpretations of the Jews. In 2 Thess. 2:15; 3:6, it is used in a good sense. Peter (1 Pet. 1:18) uses this word with reference to the degenerate Judaism of the "strangers scattered" whom he addresses (comp. Acts 15:10; Matt. 15:2-6; Gal. 1:14).