How Do You Pluralize 'Cyclops'?
First, let's talk about plurals in general. The plurals of most English words are formed by adding -s to the singular. If the noun ends in -s, -x, -z, -ch, or -sh, so that an extra syllable must be added in order to pronounce the plural, -es is added. If the noun ends in a -y preceded by a consonant, the -y is changed to i and -es is added. So we have bosses, anticlimaxes, blitzes, churches, calabashes, and allegories (which, incidentally, would make a great podcast title). In addition, the plurals of proper nouns are usually formed with -s or -es (as in "The Websters and the Joneses are joining us for dinner"), and names of creatures often have a plural formed with a suffix or one that is identical with the singular (as in lions and sheep).
With that grammar laid out, the plural of Cyclops, which is a proper noun ending in -s that denotes a mythical giant creature, should be either Cyclopses or Cyclops—but usage evidence doesn't concur. The most common plural form of Cyclops (which is now frequently found in lowercase) is Cyclopes (pronounced \sye-KLOH-peez\).
"Mythic Creatures" features models of specimens from the American Museum of Natural History and other museums' collections as well as cast fossils of prehistoric animals that tell the story of how, through misidentification, speculation, fear or imagination, they inspired legends of dragons, griffins, cyclopes and others.
— The Woodford (Illinois) Times, 27 June 2018
On the fourth field, Richland Outreach Center is hosting activities for kids, including face-painting, prizes and the Cyclops field mascots, which are actual cyclopes.
— Emily Mills, The Mansfield (Ohio) News Journal, 16 Nov. 2017
To understand the origin of this plural, we must turn to the word's romantic history.
Cyclops is a name that refers to a member of a race of giants in Greek mythology with a single eye in the middle of the forehead. Some of them worked at the forge for Hephaestus, the god of fire, forging the thunderbolts that enabled Zeus to defeat the Titans. According to one legend, the Greek god Apollo destroys the Cyclopes after one of their thunderbolts kills Asclepius (Apollo's son). The most famous Cyclops is Polyphemus, who appears in Homer's Odyssey. In the epic poem, he brutally devours several of Odysseus' men when they enter his cave; Odysseus escapes by blinding him.
Etymologically, the name is from Latin and Greek and translates as "round-eyed." When it was borrowed into the Romance languages, the -s ending was modified to one terminating in -e. Thus, we have Italian and Spanish Ciclope, and French Cyclope (the form Cyclop also occurs in early English use). The major influence of the untraditional English plural form of Cyclops as Cyclopes is suspected to be a pluralization of the French word—in particular because of the similar "y" spellings in French and English.
But true to form, English is a dynamic language that is constantly evolving and is not unresistant to change, so don't be surprised if you see the traditional Cyclopses (be leery of Cyclopses in the flesh, though).
His wiliness on the battlefield helped the Greeks win the Trojan War, and his cleverness at sea helps him topple giant Cyclopses….
— Arlice Davenport, The Witchita (Kansas) Eagle, 25 Oct. 2014
As evinced above, the -es plural form is used—but it is considered a monstrosity to many, especially fans of the mythical Cyclops, and it is often criticized. The plural form cyclops can also be found in science in reference to a group of freshwater predatory crustaceans that have a single eye, which include water fleas. The water flea has been known to transmit the Guinea worm to humans, so please keep one eye open when in the water—especially because this cyclops could be singular or plural.