What is the X in X-mas?
Babylonian and Assyrian god (identified with Adon), probably from Babylonian Du'uzu, contraction of Dumu-zi "the son who rises," also interpeted as "the faithful son."
a corruption of Dumuzi, the Accadian sun-god (the Adonis of the Greeks), the husband of the goddess Ishtar. In the Chaldean calendar there was a month set apart in honour of this god, the month of June to July, the beginning of the summer solstice. At this festival, which lasted six days, the worshippers, with loud lamentations, bewailed the funeral of the god, they sat "weeping for Tammuz" (Ezek. 8:14). The name, also borrowed from Chaldea, of one of the months of the Hebrew calendar.