What is the X in X-mas?
1530s, back-formation from Middle English myxte (early 15c.) "composed of more than one element, of mixed nature," from Anglo-French mixte, from Latin mixtus, past participle of miscere "to mix, mingle, blend; fraternize with; throw into confusion," from PIE *meik- "to mix" (cf. Sanskrit misrah "mixed," Greek misgein, mignynai "to mix, mix up, mingle; to join, bring together; join (battle); make acquainted with," Old Church Slavonic mešo, mesiti "to mix," Russian meshat, Lithuanian maišau "to mix, mingle," Welsh mysgu). Also borrowed in Old English as miscian. Related: Mixed; mixing.
1580s, "act of mixing," from mix (v.).
(often the mix) A mixture; combination of components; medley: most important element in an auto maker's marketing mix/ I enjoy what callers bring into the mix (1959+)verb
To fight; mix it: Them last two babies mixed many times a month (1921+)