Regime
late 15th century (in the sense ‘regimen’): French régime, from Latin regimen ‘rule’ (see regimen). Sense 1 dates from the late 18th century (with original reference to the Ancien Régime).
wiktionary
Borrowed from French régime, from Latin regimen(“direction, government”). Doublet of regimen.
etymonline
regime (n.)
"system of government or rule, mode of management," 1792, from French régime, from Old French regimen (14c.), from Latin regimen "rule, guidance, government, means of guidance, rudder," from regere "to direct, to guide" (from PIE root *reg- "move in a straight line," with derivatives meaning "to direct in a straight line," thus "to lead, rule").
Earlier "course of diet, exercise" (late 15c.), a sense now pertaining to regimen (q.v.). In French, l'ancien régime refers to the system of government which prevailed before the revolution of 1789.
