1520s, "to strike obliquely" (against something), alteration of slenten "slip sideways" (c.1300), perhaps via a Scandinavian source (cf. Swedish slinta "to slip," Norwegian slenta "to fall on one side"), from Proto-Germanic *slintanan. Intransitive sense of "to slope, to lie obliquely" is first recorded 1690s; transitive sense of "to give a sloping direction to" is from 1805. Related: Slanted; slanting. As an adverb from late 15c.; as an adjective from 1610s. Slant rhyme attested from 1944.