What is the X in X-mas?
1838, American English, some kind of alcoholic drink, of unknown origin. One of that class of words (e.g. dingus, doohickey, gadget, gizmo, thingumabob) which are conjured up to supply names for items whose proper names are unknown or not recollected. Used at various periods for "money," "a professional tramp," "a muffin," "a typographical ornament," "male genitalia," "a Chinese," "an Italian," "a woman who is neither your sister nor your mother," and "a foolish person in authority." Popularized in sense of "foolish person" by TV show "All in the Family" (1971), though this usage dates from 1905.
[first sense fr German or Dutch dinges, ''thing''; second sense fr Australian have the dingbats, be dingbats, ''be crazy'']