concordat (n.)

"agreement between church and state on a mutual matter," 1610s, from French concordat (16c.), from Medieval Latin concordatum, noun use of Latin concordatum, neuter past participle of concordare "to agree," from concors (genitive concordis) "of one mind" (see concord (n.)).

The most celebrated modern concordat is that concluded in 1801 between Napoleon Bonaparte as first consul and Pius VII., defining the restored privileges of the Roman Catholic Church in France, and regulating in detail the relations between the ecclesiastical and civil powers. [Century Dictionary]