The widely accepted meaning of this character is that the characters for female child were put together to form a compound because it was good for a woman to have a child. Similarly, it has been proposed that the compound originally refers to the mutual affection between the mother and child, which then extended to mean "good". These theories are supported by the smaller 子 found in some oracle bones and bronze inscriptions.
However, broader interpretations of the second character 子 could lead to other theories. 子 could also mean "son", so it may have meant two children, a boy and a girl next to each other, which is a good fortune to have a boy and a girl. 子 could also mean "man", so it may have referred to the love between a man and a woman, which is good.