What is the X in X-mas?
c.1300, las "a blow, a stroke," later "flexible part of a whip" (late 14c.), possibly imitative. The verb might be the source of the noun.
"bind," 1620s, originally nautical, from Middle French lachier, from Old French lacier "to lace" (see lace (v.)). Related: Lashed; lashing.