Why is the ninth month called September?
c.1600, "tendency," of habits, pursuits, etc.; 1640s as "state of being self-addicted," from Latin addictionem (nominative addictio) "an awarding, a devoting," noun of action from past participle stem of addicere (see addict). Earliest sense was less severe: "inclination, penchant," but this has become obsolete. In main modern sense it is first attested 1906, in reference to opium (there is an isolated instance from 1779, with reference to tobacco).
addiction ad·dic·tion (ə-dĭk'shən)
Habitual psychological and physiological dependence on a substance or practice beyond one's voluntary control.