’Adam now “knows” Eve*. The previous nude/naked distinction is clarified as a stage prior to sexual intercourse. This is where physical multiplication begins.
This concept of knowing has clear connections to a legitimate, paid-for, transaction—as distinguished from consensual happenstance or rape. This sets us on a continuing trail of distinguishing legitimate and non-legitimate (clean and unclean) sexuality. Such clarifications can assist individuals and their cultural context in finding a more whole and even holy experience of sexuality as a blessing beyond a gift. At the same time it can bedevil individuals and societies with false dichotomies and choices such as accepting one sexual orientation as legitimate and clean, excelling all others. It can also confuse categories of sex and love which can mix as chaotically as any other attempt at unifying that which cannot ultimately be joined together.
So it is two become both two, “’Adam and Eve*,” and one, “Cain.” And three become four with the multiplication continuing with “Abel.”
Remembering that Eve* was rib-constructed rather than clay-shaped, the naming of Cain continues the constructed imagery with Eve*’s announcement of having “made” a next maker (“smith”) who will make even more. Eve* claims she is partnering with G*D in making more, multiplying. We may even remember a distinction between name sources and the questionable value of etymology.
There is no such drawn out naming for a second child and this would be a good place to review your notes on family systems and where birth rank enters the conversation. Inquiring minds still want to know and so scholars have noted the similarity of Abel to another Hebrew word meaning “vapor” or “puff of air”—here today, gone tomorrow. This works as foreshadowing a short life but doesn’t address the connection with sheep (as distinct from Cain’s following the way of a tiller-of-the-soil and the valuing of connections with g()d—both intrinsic and extrinsic.