An old Northern European custom was that, during their first month of marriage, the man and woman would drink a cup of honeyed wine, which is called mead. It was considered to help with both the virility in men and the fertility in women. This honeyed wine would eventually pen the "honey" in a honeymoon. Now, since at that time in history they used a lunar calendar, a moon and a month were looked at in the same light, hence the "moon" in honeymoon. This is according to some accounts, anyway.
Many 16th and 17th Century poets compared the lunar cycle with the love of newlyweds. Just as the moon becomes full one day and begins to wane the next, so too the strength of love between newlyweds and it's eventual waning. According to Wikipedia (I know, I'm sorry), the first literary mention of a honeymoon is in 1552, in Richard Huloet's Abecedarium Anglico Latinu. He writes: "Hony mone, a terme proverbially applied to such as be newe maried, whiche wyll not fall out at the fyrste, but thone loveth the other at the beginnynge excedyngly, the likelyhode of theyr exceadynge love appearing to aswage, ye which time the vulgar people cal the hony mone." (Honeymoon, a term proverbially applied to the newly-married, who will not fall out at first, but they love the other at the beginning exceedingly, the likelihood of their exceeding love appearing to assuage; this time is commonly called the honeymoon).
Anyway, another possible origin dates back to an ancient Nordic tradition, where the husband would kidnap his wife-to-be from her village, and hide her from her family. Their friends would know their whereabouts, but would keep it a secret from the bride's family. The two, bride and groom, would stay hidden until her family stopped looking for her, which is when the groom would return to his family. During this kidnapping procedure (in some accounts), the father of the groom would provide the mead. This earliest known instance of this mead drinking during a honeymoon goes back to Atill, the Hun back in the 5th century C.E.
I hope this answers any questions my inquirers Drama class has on the origins of honeymoons. Surely, the holiday newlyweds celebrate nowadays is much, much different.
Very glad to hear questions, comments and/or opinions on my entries, and even more so when they give me topics of interest I can do a little research on. Just to be clear, said inquirer is also a good friend, but nonetheless, I'd like to hear from you.