There are nine planets in our solar system. Or is it eight? I think we’re back up to nine. Doesn’t matter. The ancients had seven “planets.” I put “planets” in quotation marks because the ancients’ list of planets included the sun and the moon (and didn’t include Earth). The word planet derives ultimately from the Greek verb planan, “to wander.” The planets were the heavenly bodies that appeared to wander across the sky, as opposed to the stars, which were (relatively) fixed.

Seven of these wanderers are visible to the naked eye:

  • the moon
  • Mercury
  • Venus
  • the sun
  • Mars
  • Jupiter
  • Saturn

These seven planets, each associated with a god or goddess, were believed to have an influence on human personalities. Those born under the planet Mercury were mercurial, those who were born under the planet Jupiter (Jove) were jovial, etc.

Perhaps I should put the word “believed” in quotation marks too: I don’t have any idea how much the average ancient Greek or Roman actually believed in planetary influence. But the system is fun and interesting to think about, and it has quite a bit of poetry in it. And it provides us with some interesting words that I thought you might find interesting to explore, planet by planet.

The Moon (Luna)

The moon was personified by the Roman goddess Luna. The adjective lunar, of course, refers to anything moon-related. The moon is both the closest and the most changeable of the heavenly bodies. Each night’s moon looks a little different from the previous night’s moon. It was believed that bodies beyond the moon were unchanging and unchangeable. But below the moon, everything changes. That’s where the word sublunary comes from. Sublunary things—that, is, everything beneath the moon—is earthy, changeable, not perfect and immutable like the superlunary world.

The highly erratic Luna also made people insane. A lunatic is a person who has fallen under her influence. The word loony comes from the same place.

The Greek equivalent of Luna was Selene. As far as I can tell, Selene doesn’t figure into the English lexicon.


Mercury, the namesake of the planet, was the messenger god, always zooming around from one place to another, never keeping still. A mercurial personality is impulsive, unpredictable, tending to change directions and change again at a moment’s notice. If you’ve ever seen the element mercury, the way it wiggles and zips around and splits into smaller beads and re-forms into larger beads, you have a good visual image of what mercurial means. (You will also know why the element mercury’s other name is quicksilver.)

Mercury’s Greek name was Hermes. The word hermaphrodite is a mashup of Hermes and Aphrodite. A hermaphrodite has characteristics of both the male (Hermes) and the female (Aphrodite).


Speaking of Aphrodite, the planet Venus is named for Aphrodite’s Roman counterpart. Aphrodite/Venus was the goddess of beauty, love, and desire. The word venereal doesn’t get used much any more, having been replaced by “sexually transmitted” in most of the applications I’m familiar with. You might be interested, however, to know that the words venerable and veneration come from the same root. A venerable person is “accorded a great deal of respect, especially because of age, stature, or wisdom.” Veneration is the respect or worship one pays to such a person. The connection is the idea of love, beauty, and desire. The qualities that we venerate are qualities that we love and find beautiful. Consider the verse, “Worship the Lord in the beauty of his holiness.”

Venery is an obsolete word for hunting. The quarry is an object of desire that the hunter pursues. Venison is meat that one gets by hunting rather than by animal husbandry.

The Sun (Sol)

Given the importance of the sun, I’m a little surprised at how few English words have sol as their root. There is solar, of course, meaning anything sun-related. A solarium is a sunroom. The solar plexus is an interesting derivative. It’s a jumble of nerves and ganglia at the pit of your stomach; that concentration of nerves accounts for why it hurts so badly when you get gut-punched. It’s called the solar plexus because the nerves radiate out from the center like the rays of the sun. (Plexus means “braid” or “network.”)


Mars, the red planet, was named for the Roman god of war. The word martial means “warlike” or “related to the military”—as in martial law. The word marshal, however, has nothing to do with Mars or martial law, even though a marshal enforces the law. Ultimately of proto-Germanic origin, marshal means literally “horse-servant”: markhaz (“horse,” as in “mare”) + skalkaz (“servant”).

Jupiter (Jove)

Jupiter, the largest planet, was named for the king of the Roman gods. Jove is a form of Jupiter. A person born under the planet Jupiter, therefore, was believed to be jovial—cheerful and friendly. This may be perplexing if you think of Jove mostly as a thunder-god, as his Greek equivalent Zeus is often portrayed. But if Mars is ascendant in times of war, Jove is the god who rules when the the work of Mars is done, when peace and prosperity, feasting and gladness prevail.

In his poem “The Planets,” C.S. Lewis describes the reign of Jove in a way that makes it clear why joviality is associated with merriment and good humor:

Of wrath ended
And woes mended, of winter passed
And guilt forgiven, and good fortune
Jove is master; and of jocund revel,
Laughter of ladies. The lion-hearted,
The myriad-minded, men like the gods,
Helps and heroes, helms of nations
Just and gentle, are Jove’s children,
Work his wonders. On his white forehead
Calm and kingly, no care darkens
Nor wrath wrinkles: but righteous power
And leisure and largess their loose splendours
Have wrapped around him – a rich mantle
Of ease and empire.


Of the seven planets that were visible to the ancients, Saturn was the coldest, the darkest, the most distant, and the slowest moving. Saturn was the oldest of the Roman gods, the father of Jupiter and several other of the major gods. A saturnine disposition, therefore, is gloomy, sluggish, given to dark moods. It may seem counterintuitive, then, that a saturnalia is a wild and decidedly un-gloomy and un-sluggish party. But in ancient Rome, the Saturnalia was a festival celebrating Saturn around the winter solstice, the gloomiest, darkest time of year. Saturday, as you may have suspected already, was named for Saturn as well.

The Roman god Saturn was associated with the Greek god Cronus. Cronus, surprisingly, had nothing to do with the cronut, which, according to this Wikipedia article, wasn’t invented until 2013. Even more surprisingly, Cronus had nothing to do with Kronos or Chronos, the personification of Time in Greek mythology. Chronos (but not Cronus) gave rise to such words as chronometer (a timepiece), chronicle (a record of the times), chronology (a timeline), chronic (describing an ailment that lasts over time), anachronism (a timeline mistake, such as the kilts worn in Braveheart, a story set about 400 years before kilts were invented) and even crony (one who has been a friend for a long time).

The other planets

Uranus, Neptune, and Pluto aren’t visible to the naked eye, so they don’t figure into ancient or medieval cosmology and astrology. That is surely the reason there are no uranian, neptunian, or plutonian personalities as there are mercurial, jovial, and saturnine personalities.

Uranus was discovered in 1781. About the only Uranus-related word in our language is the element uranium, which was discovered eight years after the planet Uranus, in 1789. Uranus, by the way, was a Greek rather than a Roman god. His Roman equivalent was Caelus, the sky-god. Hence the words for sky in French (ciel), Spanish (cielo), and Italian (also cielo). Derivatives of Caelus in English include celestial (heavenly), cerulean (sky blue), ceiling, and the names Celia, Celeste, Celine, and (I think) Selina.

The planet Neptune was discovered in the 1840s. Neptune hasn’t given us any English words, as far as I know, except for the element neptunium. Chemists gave it that name because it is right next to uranium on the periodic table, just as Neptune is right next to Uranium in the solar system. Chemists can be so clever.

That brings us to the embattled planet/dwarf planet Pluto, named for the Roman god of the underworld. Pluto is the source of the English word plutocracy, “government by the wealthy.” What, you may wonder, do the wealthy have to do with Pluto, god of the underworld? The underworld is where all gold and jewels comes from. I’m reminded of that surprising moment in Paradise Lost when we discover that the fallen angels are able to mine for gold in Hell.

The narrator suggests that we shouldn’t be surprised at all:

Let none admire
That riches grow in Hell; that soil may best
Deserve the precious bane.

If you want to understand more about the idea of planetary influence and how it plays out in literature, check out Michael Ward’s book, Planet Narnia: The Seven Heavens in the Imagination of C.S. Lewis. I interviewed Michael Ward, by the way, in Season 2, Episode 24 of The Habit Podcast.