It was the accepted practice years ago, that for a month after the wedding, the bride's father would supply his son-in-law with all the mead he could drink, to aid the couple in fertility. Mead is a honey beer and because their calendar was lunar based, this period was called the honey month, hence the honeymoon.
The first literary reference to the word honeymoon was in 1552 in Richard Huloet's Abecedarium Anglico Latinum. It held that the word honeymoon, “Was a sardonic reference to the inevitable waning of love like a phase of the moon.” There is also supposedly a Norse legend about stealing the bride, but it seems a bit far fetched. And last, there is that time of year that the moon looks all golden, like honey.
There are a few more legends, but the bottom line is that no source seems absolutely certain of the real origin. Of course you heard of honeymoon salad, which is 'lettuce alone'.