Need advice on title for birth mother

Hello, It has been a while since I have posted here, but I have a question and I'd love some input from everyone. I have a 5 year old daughter who I fostered and then adopted. She is now starting to ask questions about where she came from. I am being honest with her and answering her questions without overwhelming her with more than she wants to know. My question is what suggestions do you have for referring to her birth mother. She was only a year when she was adopted so she has no memory of her. I don't want to use the term "mother" at this age, because I don't want to confuse her. I have used her name, but we know other people with that name, and I'd like to find a way to reference her that is different while being respectful. As she gets older and understands the complexities of adoption, I plan to use the phrase "birth mother" or something similar but would like another option for now.

My youngest son came home from the hospital at three days old as my foster son. We adopted him at 15 months old. He has always known he was adopted and I have always referred to her as something like the mommy who's tummy you grew in. He has never questioned that or been confused. He has a sister adopted by another family whose adoptive parents called her a Birth Mom. At the age of 3, she thought they were calling her a Bird Mom. My oldest son has the same biological mom as my youngest son and the sister and found that amusing. So he and I refer to her as his Bird Mom.

You can call her "Mom FirstName" I hadn't even really thought of that, but Littleman just sort of naturally gravitated to that. He would hear us refer to her by her first name and then one day he asked "do you mommy first name"? and it just sort of seemed to make sense and feel natural. We started using that with Mr Tickles once Mom signed voluntary TPR - He's still pretty little and not talking yet, but when we are together I will call his mom "mommy first name" and it seemed non-threatening to his mom and just kind of worked.

i agree with PP. mom and first name works at that ageWhen we got J, she was 5. She was able to know the difference between Mummy T and me. Honestly, I think its the adults who get good luck!