Claims to the effect "it is not known that p" are rather easy for us to affirm if we ourselves don't know, and have an inherent plausibility that claims to the effect that "it is known that p" do not as often have. But it could, for all I know, be false that no one knows the origin of the word "honeymoon" or of the institution of the honeymoon more or less as it is now conceived; maybe historians or others who know about such stuff could tell us definitively. --LMS
I had always heard the explanation for the name as first documented from an old middle english book, however it is usually commented that this is the first "documented" record of a practice called the "honeymoon". Since the meaning is referred to rather than word coined, I would assume it was in at least some common use by the time the author wrote about it. Some nonauthoritative internet sources have claimed the honey mead story to be false.
As for the origination of the practice, there are several mutually contradictory sources going around.
If someone states emphatically that they know the origin of the word or the practice, I would prefer some documentation backing it up, since no one else on the internet seems to have any. In the meantime, perhaps "disputed" is a better word? --Alan D
To ease decipher the origins, maybe it's helpful to look at a few more languages for this expression. In Hungarian, the appropriate words are mézeshetek, approx. "weeks of/with honey". In German, it's Flitterwochen, "glittering? weeks". It's easily conceivable that the -moon can refer to either the waning and of affection, or the duration itself. After all, Month also stems from Moon, in many languages. Honey- can easily refer to the sweetness/greatness of the new love, or some actual food/drink of honey. From these three languages, the greatness/sweetness meaning looks favorable for honey-, and the timespan meaning for -moon. But of course it's uncertain who borrowed from who, or that there is a single "real" origin at all.