Shady

People use the term shady to call out other people's suspicious, dishonest, or otherwise disreputable behavior. People and actions can both be labeled as shady. For example, a used car salesman trying to sell you a stolen car is a shady person conducting a shady deal.

Where did shady come from?

People who perform illicit actions often prefer to do so under the cover of darkness. These people's preference for the "shade" is what caused them and their actions to be labeled shady.

Does "being shady" have anything to do with "throwing shade?"

Not really. While the terms are similar, "being shady" has next to nothing to do with "throwing shade."