I'm not aware of a widely - known 'wife swallows story' in mainstream literature or common folklore. There might be some very specific regional or personal stories with this name, but nothing that comes to mind as globally famous.
To overcome nervousness when it comes to the first time swallowing cum, first, make sure you're in a comfortable and safe environment. This means you trust your partner completely. Build up your confidence by exploring other aspects of sexual intimacy first. Get used to the physical closeness and the overall sexual atmosphere. Also, focus on the positive aspects of the act within the context of your relationship, such as showing love and acceptance to your partner. But always remember that your feelings and boundaries are important, and if you're not ready, it's perfectly fine to wait.