slat n.

c. 1200, slitten, "to split with a knife or sharp weapon, cleave open," from or related to Old English slitan "to slit, tear, split, rend to pieces; bite, sting; back-bite," from Proto-Germanic *slitanan "tear apart" (source also of Old Saxon slitan, Old Frisian slita, Old Norse slita, Middle Low German and Middle Dutch sliten, Dutch slijten, Old High German slizan, German schleißen "to slit"). Slice is the same word via French.

A more violent verb in Old English than after, as in slitcwealm "death by rending." From late 14c. as "make an incision."

Slit skirt, one tight and with a slit or slits up from the hem, is by 1913 (as an adjective, slit, in reference to garments decorated with slashes, is from late 14c.). A slitting-mill (1660s) cut iron plates into thin rods for making nails, etc.

1540s, intransitive, "to make cuts or cutting motions with a stroke of a blade or whip;" 1580s, transitive, "cut with long incisions;" perhaps from French esclachier "to break," variant of esclater "to break, splinter" (see slat).

Attested from 1650s as "to strike violently or at random." The meaning "to clear land" (of trees) is from 1821, American English. In reference to prices, "reduce severely," it is attested by 1876 in U.S. newspaper advertisements. Related: Slashed; slashing. Slash and burn for a method of clearing forest for cultivation is by 1887.

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.