side hustle

[keannu]

https://www.idiomsandslang.com/side-hustle/

I’m an accountant, but I have a side hustle designing and marketing cards.

1. What is the origin of "side hustle"?
2. What does this mean? What kind of cards does he or she make?
designing and marketing cards.

[probus]

1. It is pretty recent slang. See the Wikipedia article on Side Job.

2. We don't know without more context. They could be greeting cards, business cards, or any kind of cards. And she or he doesn't actually make them, only designs and markets them. Presumably a printer makes them.