I was actually reading this weekend (oooo…ahhhh), and oh-so-enjoying losing myself in the pages of a fine historical. A fine historical that at one point made me pause when these 1866 characters used the word sketchy.
Insert Roseanna narrowing her eyes and scratching her head. And being word-nerd enough to pause and go, “Really? I trust this author and publisher, but…really?”
Da Vinci, Head of a Woman sketch
So naturally I had to look it up. =) 
And indeed, sketchy was a word by then. By, in fact, 1805. At which point it had a literal meaning of “sketch + y” says www.etymonline.com. Which made me scratch my head again, because I’ve honestly never heard it used in a literal sense. So I hop over to dictionary.com to see what that is and discover it means (duh) “like a sketch, giving only outlines or essentials.” Which…yeah, okay. From which came the meaning of “imperfect or incomplete.” But that sense didn’t emerge until 1878.
Not sure when the informal, slang meaning of “disreputable / shady” joined the family, but that one, I’m pretty sure is more modern. And how I usually hear it used. 😉
Hope everyone had a great weekend! I’m happy to report that I’ve finished going over my galleys for Ring of Secrets and am ready to send the manuscript home to Harvest House today. =) Quite a relief, as now I can focus on preparing for conference. Woot!