I've only ever seen the term used to refer to the bags people prepare in advance for emergencies.

A go bag is a bag you keep packed for when shit hits the fan. What's in it depends on what shit you expect to hit which fan. Maybe it has survival tools and rations. Maybe it's prescription medicine and warm clothing. Maybe it's a map and some weapons. In theory, it should be only essentials, but being prepared for long stints of boredom is often a part of preparing for the worst (aka prepping). People frequently include a deck of cards or a harmonica to help pass the time, maybe a tennis ball to play fetch with their dog.

And yes, preppers will often stock a "stay bag" although the priorities are different. Mobility and weight isn't a priority, but it is still a factor. Preppers will stock water, weapons, ammo, and food, often in larger quantities, but keeping a small subset available for quick travel. For instance, they might keep 2 weeks worth of water in their home or bug out site, but the water will be in jerry cans they can throw in the trunk of a car, or carry to a stream for refills. If you plan to hunker down, then having a library of books or other low-tech forms of entertainment are recommended to help stave off the crazies.

It sounds like OP is asking for a generic sling bag, aka a purse for daily use. Like "I'm going out the door for the day, and I might find myself with some spare time to read." I haven't heard anyone call that a go bag, but maybe it's just the phrase expanding in use. I recently heard a 9 year old walking around a parking lot in bare feet say she was "out here raw dogging the pavement" and I seemed to be the only person fazed by it, so I just keep walking.

yeah i just use a backpack tbh

Lots of print options too!

That's a nice-looking bag. They're all currently sold out though.