Sketchy means giving only the outline, or not quite trustworthy. Sketchy details, a sketchy account, a sketchy neighbourhood.
The original sense is incomplete, like a sketch. The American sense of dubious or unsafe grew from it and is now the commoner one in speech, so sketchy details and a sketchy character mean quite different things.
1adjectivesketchyGiving only the outline, or not quite trustworthy.
“Reports of the accident are still sketchy, and police have released few details.”
sketchy is a quality.
Sketch plus -y, from Dutch schets, from Italian schizzo, a splash or rough drawing.
Proto-Indo-European
*seǵʰ-
Ancient Greek
σχέδιος — made suddenly, off-hand
Latin
schedium
Italian
schizzo
German
Skizze
Dutch
schets
English
sketch
English, today
sketchy
Built from
From sketch + y. Extension of "brief, imperfect, unfinished" notion. sketch comes from Dutch schets or German Skizze, from Italian schizzo, from Latin schedium, from Ancient Greek σχέδιος (“made suddenly, off-hand”), from σχεδόν (“near, nearby”), from ἔχω (“to hold”). Compare scheme.
Etymology from Wiktionary, CC BY-SA