What is the X in X-mas?
1801, "given to cutting a dash" (1786), which was a colloquial expression for "acting brilliantly," from dash (n.) in the sense of "showy appearance," which is attested from 1715. The sense of "splashing" is recorded from mid-15c.
c.1300, probably from a Scandinavian source (cf. Swedish daska, Danish daske "to beat, strike"), somehow imitative. The oldest sense is that in dash to pieces and dashed hopes. Intransitive meaning "move quickly" appeared c.1300, that of "to write hurriedly" is 1726. Related: Dashed; dashing.
late 14c., from dash (v.). Sporting sense is from 1881, originally "race run in one heat."
A punctuation mark (—) used to indicate a sudden break in thought, to set off parenthetical material, or to take the place of such expressions as that is and namely: “He's running for reelection — if he lives until then”; “Very few people in this class — three, to be exact — have completed their projects”; “She joined the chorus for only one reason — she loves to sing.” In the last example, where the parenthetical material comes at the end of the sentence rather than in the middle, a colon could be used instead of the dash.
The dashboard of a car or other vehicle: I keep a gun under the dash (1867+)Related Terms