I remember reading an excerpt in a book called A Shining Affliction about wanting to be little. It was written by a psychologist about her own experience of trauma and therapy, and also working as a therapist with traumatized children.

She would bring a stuffed rabbit (I think) to sessions with her T, and on one occasion her T was holding the rabbit to his chest, the way one would hold an infant. He was whispering in the rabbit's ear and soothing it, again, in the way one would interact with a small child. The author wrote that her only wish when she was little and being abused by her mother was that she could stay small so that someday, someone could care for her in the way her T cared for her bunny.

I think being little can be about being vulnerable in an innocent, pre-trauma way. Holding wonderment about the world in a way that is untarnished by the pain and fear of trauma. Trust is in there too, that the person you're with won't harm you, has your best interests in mind.

I hope you find the caring and protection you're seeking.