1540s, "to cut with a stroke of a blade or whip;" 1650s, "to strike violently," perhaps from French esclachier "to break," variant of esclater "to break, splinter" (see slat). Meaning "to clear land" (of trees) is from 1821, American English. In reference to prices, it is attested from 1906. Related: Slashed; slashing. Slash-and-burn for a method of clearing forest for cultivation is from 1919.
<a href="https://www.etymonline.com/word/slasher">Etymology of slasher by etymonline</a>
Harper, D. (n.d.). Etymology of slasher. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/slasher