"rough drawing intended to serve as the basis for a finished picture," 1660s, from Dutch schets or Low German skizze, both apparently 17c. artists' borrowings from Italian schizzo "sketch, drawing," which is commonly said to be from Latin *schedius (OED compares schedia "raft," schedium "an extemporaneous poem"), from or related to Greek skhedios "temporary, extemporaneous, done or made off-hand," related to skhema "form, shape, appearance" (see scheme (n.)). But according to Barnhart Italian schizzo is a special use of schizzo "a splash, squirt," from schizzare "to splash or squirt," of uncertain origin.
Extended sense of "brief account" is from 1660s; meaning "short play or performance, usually comic" is from 1789. Sketch-book recorded from 1820. German Skizze, French esquisse, Spanish esquicio are likewise from Italian schizzo.
1690s, "present the essential facts of," from sketch (n.). Meaning "draw, portray in outline and partial shading" is from 1725. Related: Sketched; sketcher; sketching.