"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 .