slate n.

mid-14c. (c. 1300 in Anglo-Latin), sclate, "tile or slate used principally in roofing," from Old French esclate, fem. of esclat "split piece, splinter" (Modern French éclat; see slat). So called because the rock splits easily into thin plates.

As an adjective, 1510s. As a color, by 1813 (slate-gray is from 1791 in dyeing, later in bird descriptions; slate-colour is from 1743, slate-blue from 1792).

The sense of "a writing tablet" (made of slate), is recorded by late 14c. and led to that of "list of preliminary candidates prepared by party managers," attested from 1842, from notion of being chalked on a slate and thus easily altered or erased. Clean slate "fresh beginning of a state of affairs" (1856) is an image from customer accounts chalked up in a tavern.

1520s, "to cover with slates," from slate (n.). The earlier form was sclatten (late 15c.), and compare slater. The meaning "propose, schedule" is from 1883; earlier "to nominate" (1804); the notion is of writing on a slate board. Related: Slated; slating.