English word injustice comes from Latin iniustus, and later Latin iniustitia (Injustice, unfairness, inequity.)

Detailed word origin of injustice

Dictionary entry	Language	Definition
iniustus	Latin (lat)	Severe, excessive (punishment). Unjust, wrongful. Unsuitable.
iniustitia	Latin (lat)	Injustice, unfairness, inequity.
injustice	Old French (fro)
injustice	English (eng)	Absence of justice; unjustice.. Unfairness; the state of not being fair or just.. Violation of the rights of another person.