Yeah, it does seem to be lost. Wiktionary has a couple theories. Here’s the first one:
The widely accepted meaning of this character is that the characters for “female” (女) and “child” (子) were put together to form a compound because it was good for a woman to have a child.
The app hello Chinese said it’s because having a wife and a child is good, lol
I guess the original meaning is lost in 5000 years of history.
Yeah, it does seem to be lost. Wiktionary has a couple theories. Here’s the first one: