mid-14c., "act or fact of possessing, a taking possession, occupation," also "thing possessed, that which is possessed," from Old French possession "fact of having and holding; what is possessed;" also "demonic possession," and directly from Latin possessionem (nominative possessio), noun of action from past participle stem of possidere "to possess" (see possess). Legal property sense is earliest; demonic sense first recorded 1580s. Phrase possession is nine (or eleven) points of the law is out of a supposed 10 (or 12). With eleven from 1640s; with nine from 1690s.
St. Jerome in his 'Life of St. Hilarion' has given us a graphic account of the courage with which that saint confronted, and the success with which he relieved, a possessed camel. [Lecky, "History of European Morals"]