What is the X in X-mas?
late 14c., "act of attending to one's duties," from Old French atendance "attention, wait, hope, expectation," from atendant, present participle of atendre (see attend). Meaning "action of waiting on someone" dates from late 14c. (to dance attendance on someone is from 1560s); that of "action of being present, presenting oneself" (originally with intent of taking a part) is from mid-15c. Meaning "number of persons present" is from 1835.