Write sorry letter to girlfriend, the basic primer
You can find a very cute name from cartoon characters you used to watch, toys and other fun stuff from childhood. Another category is the memorable times category. Now this is easy because you will simply have to remember a particularly lovely time together and take inspiration from there. For example, if you went to the park and she kept looking and touching the flowers, you can call her bumble bee. The most commonly used one and another good source of inspiration is food.