You were named Umm Muiminin only so that you might be blessed, and indeed it was your name before you were born.
حدثنا سفيان عن ليث عن رجل قال
إنما سميت أم المؤمنين لتسعدي وإنه لاسمك قبل أن تولدي
Its isnad is daif, due to the unknown identity of the narrator who reported from Ibn Abbas. It follows the one before it, and is a repetition of 1906 with this same isnad.