Riley /ri-ley/ [2 sylls.] as a girls' name (also used less commonly as boys' name Riley) is pronounced RY-lee. It is of Irish and Gaelic origin, and the meaning of Riley is courageous.Variant of O'Reilly. Lately adopted for girls and boys.iley is an unusual first name for women but a very prominent surname for all people (#210 out of 150436, Top 1%). (2000 U.S. Census). Charted below is the baby name popularity of Riley for girls.