Bundle of joy

What is the origin/likely derivation of "bundle of joy", referring to a baby (born or yet-to-be-born)? On the simpler, more innocent side, it could be merely from "bundle" as a "package" and "joy" as "happiness". On the more complex, less innocent side, it could be related to the use of "bundle" to refer to a woman, especially a fat one, and/or to "bundle" or "bundling" as in the old courtship ritual. Nothing in OED about this.

I vote for innocence.

I vote similarly. Because babies are often swaddled in blankets when out of bed, they look like bundles.