shady

Etymology

From shade + -y. Compare Saterland Frisian skaadich, skaddich (“shady”), German schattig (“shady”).

adj

1. Abounding in shades.
2. Causing shade.
3. Overspread with shade; sheltered from the glare of light or sultry heat.
4. (informal) Not trustworthy; disreputable.
   He is a shady character.
   2009: Stuart Heritage, Hecklerspray, Friday the 22ⁿᵈ of May in 2009 at 1 o’clock p.m., “Jon & Kate Latest: People You Don’t Know Do Crap You Don’t Care About” Jon & Kate Plus 8 is a show based on two facts: 1) Jon and Kate Gosselin have eight children, and 2) the word ‘Kate’ rhymes with the word ‘eight’. One suspects that if Kate were ever to have another child, a shady network executive would urge her to put it in a binbag with a brick and drop it down a well. But this is just a horrifying tangent.
5. (UK, slang) Mean, cruel.
   Don't be shady, give us a go.
   They were being proper shady to him. Even if you don't like someone, locking them out, stealing their clothes and ganging up on them to take the piss is just childish. 2006-05-24, Saucy Jack, “BB7: Did Shabazz just deserve that?”, in uk.media.tv.misc (Usenet)
   I didn't even ask her to be in the 'Increase the Peace' campaign, which was well shady, 'cos if anyone knows anything about rudes and violence and getting dragged into stuff it's Uma. 2007, Grace Dent, Diary of a Chav 2: Slinging the Bling
   "Don't be shady," she said, "You know I always pay up." 2007, Chastity Danielle Infinity, Jamo Lorswal, A Rose So That It May Rain, page 155