monarchy (n.)

mid-14c., monarchie, "a kingdom, territory ruled by a monarch;" late 14c., "rule by one person with supreme power;" from Old French monarchie "sovereignty, absolute power" (13c.), from Late Latin monarchia, from Greek monarkhia "absolute rule," literally "ruling of one," from monos "alone" (from PIE root *men- (4) "small, isolated") + arkhein "to rule" (see archon). Meaning "form of government in which supreme power is in the hands of a monarch" is from early 15c.