Yours, Etc.: Origins and Uses of 8 Sign-Offs
c.1400, medical, "course of diet, exercise, etc. for sake of health;" mid-15c., "act of governing," from Old French regimen (14c.), from Latin regimen "rule, guidance, government, means of guidance, rudder," from regere "to rule" (see regal).
regimen reg·i·men (rěj'ə-mən, -měn')
A regulated system, as of diet, therapy, or exercise, intended to promote health or achieve another beneficial effect.
A course of intense physical training.