1885, "to stimulate toward action," from motive (q.v.), perhaps modeled on Fr. motiver or Ger. motivieren.Motivation first recorded 1873; the psychological sense of "inner or social stimulus for an action" is from 1904.
Main Entry: mo·ti·vate Pronunciation: 'mOt-&-"vAt Function: transitive verb Inflected Forms: -vat·ed; -vat·ing : to provide with a motive or serve as a motive for —mo·ti·va·tive/-"vAt-iv/adjective
[moh-tuh-veyt] 
təˌveɪt