"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.
"take a wedding trip," 1821, from honeymoon (n.). Related: Honeymooned; honeymooning; honeymooner. The first TV "Honeymooners" sketch aired in 1951.