While without a doubt the brand is important that comes after you have created a good casino, after all it can be a huge issue if you named your casino in a way to it is too similar to another casino that was known for scamming their customers.
Also the name has to be short and it has to be catchy so people can easily remember, however while this is important the functionality of the casino is even more important as without that no one will be interested in playing at that casino at all.
I think that before a casino creates a name, they will first research the name if there are any gambling sites with a name that is close to it. If ever there are, they will skip that and will try to look for a more unique name. This could be the reason why many casinos have a weird name or names that aren't totally related to gambling or to their website.
We didn't realize the pain that they gone through before they end up a name like that so we must respect it. Even if the name is not catchy, people can still remember it as long as they are already hooked on playing on that casino. Functionality is going to be next to it so the answer to the op's question is both.