que significa "sweetiepie"?
Literalmente es: "Dulce Pastel", but we never say such thing. We would say something like: "muñeca", "corazoncito", "amorcito"
it is a term of affection. You could also say pumkin pie, or sweet pea. In spanish you might say "cielito" or "cariño"
I would think that "sweetie" would be like "muñeca," and "sweetie-pie" would be like "muñequita."
Specifically (or literally) "sweet" is dulce, and "sweetie" is a common form of endearment, like a nick name for "sweet one" pie is an empanada (filled with fruit) Sweetie pie is extra cute - can be TOO cute for some, overly sweet. Therefore, more playful, can be used with children, not just un novio o una novia. Not what most people would use in a serious moment, but more for a light and playful moment.
It is a term of affection.