The definition of the *Informal* word **"Sketchy"** is as follows: 

> **Sketchy** *[skech-ee]* 
>
> **Adjective** *Informal.*
>
>1. unreliable or unsafe:
>
>*That street looks pretty sketchy.*
>
>2. disreputable or shady:
>
>*I'd stay away from him; he's got a sketchy past.*

What is the Origin of this Usage? How does it relate to the word Sketch?

>**Sketch** *[skech]*
>
> **Noun**
>
> 1. a simply or hastily executed drawing or painting, especially a preliminary one, giving the essential features without the details.
>
>2. a brief or hasty outline of facts, occurrences, etc.:
>
> *a sketch of his life.*
>
>3.a short, usually descriptive, essay, history, or story.
>
>4.a short play or slight dramatic performance, as one forming part of a vaudeville program.

Etymonline only has the Origin of the *Formal* "Sketchy" describing an unfinished work.