Love makes you do the wacky.
—Joss Whedon and David Tyron King, “Some Assembly Required,” Buffy The Vampire Slayer, 22 September 1997
We all know that people in love sometimes act insane, and that is the concept behind the modern use of the word moonstruck. Someone who is moonstruck is out of their mind with love. But this was not always the case; the word originally simply referred to insanity. The idea that the phases of the moon could trigger mental illness is an old one—English use of the word lunatic dates to the late thirteenth century—and that’s where the concept of being moonstruck comes from.
Moonstruck first appears in John Milton’s 1674 version of Paradise Lost in a long list of ailments visited upon humanity because of Adam and Eve’s indiscretion with the apple:
Demoniack phrenzy, moaping melancholy,
And moon-struck madness, pining atrophy,
Marasmus, and wide-wasting pestilence,
Dropsies, and asthmas, and joint-racking rheums.
Milton uses the word to describe madness. (Milton’s list of afflictions is much longer than the bit quoted here; it’s a wonderfully colorful list of disease and pestilence.)
But in the mid-nineteenth century the meaning of moonstruck suddenly shifts and acquires an association with love and romance. To the Victorians, to be moonstruck was to be madly in love, combining the idea of madness with a moonlit lovers’ tryst. Charles Dickens is the first known to use the word in association with love when he describes the title character of his 1850 novel David Copperfield as “the moon-struck slave of Dora.” Shortly afterwards, Matthew Arnold, in his 1852 Tristram and Isuelt, describes Tristram as a “moonstruck knight.” The older sense of plain madness and lunacy quickly dropped away and moonstruck came to mean “in love.”
There are some other senses of moonstruck based on various superstitions about the effects of moonlight. Some believed that sleeping in moonlight can cause blindness, and those afflicted with this supposed moon-blindness were sometimes called moonstruck. Nineteenth-century sailors believed that the tropical moon would spoil fish, and said fish were said to be moonstruck. Of course, it was the tropical heat, and not the moonlight, that caused the fish to spoil, but superstition seldom has any truck with common sense. And various and sundry other afflictions were attributed to being struck by moonlight. Most of these are older uses are seldom found today, but if you look hard enough you may find them.
“moonstruck, adj.,” Oxford English Dictionary, third edition, December 2002.
Copyright 1997-2013, by David Wilton