You can’t do that as it goes against shell variable/array naming schema. I believe you can only letters and numbers including _ in bash variable names.
I will probably delete this post as it is about why arrays cannot be assigned in certain ways. The reasons are still a mystery to me and propbably always will be. And none of the books I have addresses the naming conventions of arrays in a consistent manner. So I always get tangled up with array naming as it seldom behave as expected.
So you are left to reverse engineer and test every time you need to use arrays creatively, rather than having a consistent understanding.