Sketch comes from Italian schizzo ('splash, rough drawing'), from Greek schédios ('done offhand'). A sketch was originally understood as a splash of ink — quick and impromptu, not intended as a finished work.
A rough or unfinished drawing or painting, often made to assist in making a more finished picture; a brief written or spoken account.
From Dutch schets or German Skizze, from Italian schizzo meaning 'a splash, a sketch', from Latin schedium meaning 'an extemporaneous work', from Greek σχέδιος (schédios) meaning 'done offhand, impromptu'. The Greek root σχεδόν (schedón) meant 'near, close' — something done schédios was done approximately, close to the final version but not exact. The Italian schizzo also meant 'a splash of liquid', and a sketch was originally understood as a splash of ink — quick, spontaneous, not meant to be permanent. The word entered English through
In Italian, schizzo means both 'sketch' and 'splash' — because an artist's quick drawing was seen as a splash of ink, not a deliberate composition. The English slang 'sketchy' meaning 'unreliable' preserves this: something sketchy is rough, unfinished, not to be trusted — like a drawing dashed off without care.