It was discovered in September 2005 by Mike Brown and the Laser Guide Star Adaptive Optics (LGSAO) team at the W. M. Keck Observatory.

In 2005, the adaptive optics team at the Keck telescopes in Hawaii carried out observations of the four brightest Kuiper belt objects (Pluto, Makemake, Haumea, and Eris), using the newly commissioned laser guide star adaptive optics system.

[14][7] Combining Keck and Hubble observations, the orbit of Dysnomia was used to determine the mass of Eris through Kepler's third law of planetary motion.

[2] Dynamical simulations of Dysnomia suggest that its orbit should have completely circularized through mutual tidal interactions with Eris within timescales of 5–17 million years, regardless of the moon's density.

A non-zero eccentricity would thus mean that Dysnomia's orbit is being perturbed, possibly due to the presence of an additional inner satellite of Eris.

Impacts between bodies of the order of 1000 km across would throw off large amounts of material that would coalesce into a moon.

Before receiving their official names, Eris and Dysnomia had been nicknamed "Xena" and "Gabrielle", though Brown states that the connection was accidental.

Pluto owes its name in part to its first two letters, which form the initials of Percival Lowell, the founder of the observatory where its discoverer, Clyde Tombaugh, was working, and the person who inspired the search for "Planet X".

James Christy, who discovered Charon, did something similar by adding the Greek ending -on to Char, the nickname of his wife Charlene.