First of all, the term honeymoon is significantly older than the practice of going on a holiday following a wedding. It originated in the early part of the 16th century and for a long period was nothing more but a figurative phrase to describe the strong infatuation that surrounded a marriage ... and would then go away as marriage progressed.

The practice of going on a holiday isn't recorded until the 1800s and was (at first) largely limited to the upper class. It is closely linked to the so-called Grand Tour, a custom in which young upper-class British men would go on a tour of Europe's most prestigious cultural centers following the completion of their formal education. This practice started in the second half of the 17th century, but during the 19th century; it became common for rich young women to go on a similar tour prior to marrying as well.

Honeymoons started out as a variant of the above: a prestigious, upper-class practice in which the man and woman would go on a ( yet another, though limited) trip together before the practical aspects of the marriage (child rearing, social responsibilities, etc.) would begin.

The second part of the 19th century saw the Grand Tour disappear as the beginnings of modern tourism emerged, but the honeymoon-practice remained. In a way, it could be considered a modern continuation of the Grand Tours; because (like the Grand Tour and unlike modern tourism) it retains the "Once in a lifetime" aspect.