Galilean Moons

The four Galilean Moons of Jupiter refer to the astronomer Galileo Galilei who is credited with identifiying them in 1610.They are by far the largest of the many moons of Jupiter. In order from closest they are Io, Europa, Ganymede, and Callisto. Io, Europa, and Ganymede are locked into a 1:2:4 orbital resonance, Callisto is not, but, all four moons are locked into a tidal rotation, keeping the same face toward Jupiter throughout their orbits.

Galileo first named the moons Gosmica Sidera (Cosimo's stars), but the names that caught on were given by Simon Marius who independently observed the moons about the same time as Galileo. See Galilean moons at Wikipedia.