What is the X in X-mas?
word-forming element meaning "hater, hatred," before vowels, mis-, comb. form of Greek misos "hatred," misein "to hate." Productive as a word-forming element in ancient Greek, e.g. misoagathia "hatred of good or goodness;" misoponein "to hate work." Forming many compounds in English, most of them obscure or recherche, but some perhaps useful, e.g. misocapnic (adj.) "hating (tobacco) smoke," misocyny "hatred of dogs."
miso- or mis-