Honeymoon
mid 16th century (originally denoting the period of time following a wedding): from honey + moon. The original reference was to affection waning like the moon, but later the sense became ‘the first month after marriage’.
wiktionary
From honey + moon, but the original metaphorical idea is uncertain. Perhaps a cynical comparison of a full moon to the love of a newly married couple, which starts out sweet (as honey) but then wanes (16th century), later coming to mean the first month (i.e. "moon") after marriage.
etymonline
honeymoon (n.)
"indefinite period of tenderness and pleasure experienced by a newly wed couple," 1540s (hony moone), but probably older, from honey (n.) in reference to the new marriage's sweetness, and moon (n.) "month" in reference to how long it probably will last, or from the changing aspect of the moon: no sooner full than it begins to wane. French has cognate lune de miel, but German version is flitterwochen (plural), from flitter "tinsel" + wochen "week." In figurative use from 1570s. Specific sense of "post-wedding holiday" attested from c. 1800.
honeymoon (v.)
"take a wedding trip," 1821, from honeymoon (n.). Related: Honeymooned; honeymooning; honeymooner. The first TV "Honeymooners" sketch aired in 1951.
