What is the X in X-mas?
Old English wincian "to nod, wink," from Proto-Germanic *wenkanan (cf. Dutch wenken, Old High German winkan, German winken), a gradational variant of the root of Old High German wankon "to stagger, totter," Old Norse vakka "to stray, hover," from PIE *weng- "to bend, curve." The meaning "close an eye as a hint or signal" is first recorded c.1100; that of "close one's eyes to fault or irregularity" first attested late 15c. Related: Winked; winking.
c.1300, from wink (v.); meaning "very brief moment of time" is attested from 1580s.
v. winked, wink·ing, winks
To close and open the eyelid of one eye deliberately, as to convey a message, signal, or suggestion.
To close and open the eyelids of both eyes; blink.