Moons - Trojan and Otherwise

Newly discovered moons of Saturn have been named classically (BBC; PhysOrg) [unlike some others recently found--Ymir et al.--as you can see from this factsheet]: Methone, Pallene, and Polydeuces. The first two are interesting, since they were taken from Greek place names--although maybe someone who has followed such nomenclature more closely knows better...The newly named Polydeuces is (as you might expect) one of a pair: it's a so-called "Trojan moon," which means it orbits in tandem with another body...That body, however, is Dione (not the companion you might have been expecting). The term "Trojan moon" appears to be an extension of "Trojan asteroid," which indicates a class of asteroids occupying specific points in relation to the Sun and Jupiter: in theory, those at one "Lagrangian node" are given names of Greeks associated with the Trojan war [the first-discovered of which is "Achilles"], those at another names of Trojans--but the complications continue:

Following Wolf's lead these asteroids were given names associated with the Iliad—in fact, those in the L4 point are named after Greek heroes of the Iliad (the "Greek node" or "Achilles group"), and those at the L5 point are named after the heroes of Troy (the "Trojan node"). Confusingly, the latter group are sometimes called Patroclean asteroids after the most prominent of those, even though Patroclus (the hero) was on the Greek side. However, 617 Patroclus (the asteroid) was the first discovered asteroid at the L5 point, and was named before the Greece/Troy rule was devised. The Greek node also has one "misplaced" asteroid; 624 Hektor.

As the Iliad deals with the events of the Trojan War, the asteroids came to be collectively known as Trojan asteroids. Over time, this term has come to be more generally applied to any planetoidal body at the triangular Lagrangian point of any two bodies—besides Jupiter's Trojans, Mars and Neptune have one Trojan each, plus there are Trojan moons around Saturn (Telesto–Tethys–Calypso and Dione–Helene). Strictly speaking, the term Trojan applies only to those in the L4 and L5 points of the Sun-Jupiter system.

Got that?