The origin of the word honeymoon The Oxford English Dictionary offers no etymology at all, but dates the word back to the 16th century: The first month after marriage, when there is nothing but tenderness and pleasure" (Samuel Johnson); originally having no reference to the period of a month, but comparing the mutual affection of newly-married persons to the changing moon which is no sooner full than it begins to wane; now, usually, the holiday spent together by a newly-married couple, before settling down at home One of the oldest citations in the OED indicates that, while today honeymoon has a positive meaning, the word was actually a sardonic reference to the inevitable waning of love like a phase of the moon. This, the first literary reference to the honeymoon was penned in 1552, in Richard Huloet's Abecedarium Anglico Latinum. Huleot 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 (quarrel) at first, but they love the other at the beginning exceedingly, the likelihood of their exceeding love appearing to assuage [any quarrels]; this time is commonly called the honeymoon"). It has also been said that the origin of the word is based upon the practise of newlyweds drinking mead (a honey-based drink) during the first month (and therefore "moon") of marriage. Weddings once commonly took place upon the Summer solstice and it was at this time of year that honey was first harvested. The drink supposedly increased virility and fertility. Thus the first month of marriage became a honeymoon. Retrieved from "http://en.wikipedia.org/wiki/Honeymoon"

From http://www.southsidebride.com/funfacts.htm There are 2 main concepts here ... centuries ago it was the norm for the bride's father to supply his new son-in-law with all the "mead" he could drink for a period of a month after the wedding. "Mead" is honey beer, and was believed to be the drink of a "real man" so if he could handle it, he would gain the Father's approval. This period was called "Honey-month" The calendar was based on the moon cycle during this time, which is believed to be where we get what is now known as the "Honeymoon" Another idea was that both the bride and groom would drink this "honey beer" or "honey wine" for a moon cycle (a month) in order to guarantee fertility in their marriage. Today, the honeymoon is pretty much just an excuse for a vacation and a time for the newlyweds to be alone, which in some cases could have the same "fertile" result ;-) However, unless your lucky, the honeymoon usually doesn't last a month