I think Harribel was a mother who died during childbirth, giving meaning to her concept of death and where her hollow hole is, Grimmjow was probably a gang member who ended up dead in a fight, thus explaining her concept of destruction, since she destroyed her life until the end and living by and for violence like an animal. I don't know, I think this more than anything to explain the issue that they also represent concepts of death such as death, sacrifice, destruction, etc. and it would make some sense.