Adaptation of the latin word for unbound (Solutus). The choice of unbound is one that i find fitting for several reasons. Most of the races in the ES universe were radically affected by dust and the Endless, This race was not, or at least to a lesser degree than most. Also given that they're Shadow Wraiths and an espionage faction, they lack certain restrictions that other species have. All in all I feel it is a fitting name.