Why is the ninth month called September?
late 14c., "unrestricted; complete, perfect;" also "not relative to something else" (mid-15c.), from Middle French absolut (14c., Old French asolu, Modern French absolu), from Latin absolutus, past participle of absolvere "to set free, make separate" (see absolve).
Most of the current senses also were in the Latin word. Sense evolution was "detached, disengaged," thus "perfect, pure." Meaning "despotic" (1610s) is from notion of "absolute in position." Absolute monarchy is recorded from 1735 (absolute king is recorded from 1610s); scientific absolute magnitude (1902), absolute value (1907) are from early 20c. In metaphysics, the absolute "that which is absolute" is from 1809.