They lay soe close together, they made me much to wonder;As a noun meaning "semen or other product of orgasm" it is on record from the 1920s. The sexual cum seems to have no connection with L. cum, the preposition meaning "with, together with," which is occasionally used in English in local names of combined parishes or benifices (e.g. Chorlton-cum-Hardy), in popular Latin phrases (e.g. cum laude), or as a combining word to indicate a dual nature or function (e.g. slumber party-cum-bloodbath).
I knew not which was wether, until I saw her under.
Then off he came, and blusht for shame soe soon that he had endit;
Yet still she lies, and to him cryes, "one more and none can mend it."