A Bag Holder normally describes someone that bought a currency at some price, only to see the digital asset’s price drop before he got a chance to sell it.
Now he’s stuck with a bag of worthless cryptocurrencies.
You don’t want to be a bag holder.
It usually means that your currency is worth less than what you paid for it.
Selling now would mean selling at a loss – which is bad.
As a bag holder, now you’re “holding a bag”, or “you’ve got a bag”.
Trader 1: “You get out of Luna before it crashed?”
Trader 2: “Uh, nope. I was watching Stranger Things and didn’t have a chance to sell. Now I’m stuck with a bag forever!.”