Where does the name Kelsey come from?

Kelsey \k(e)-lsey, kel-sey\ as a girl's name (also used as boy's name Kelsey), is pronounced KEL-see. It is of Old English origin, and the meaning of Kelsey is "victorious ship". Also possibly a place name referring to "island". Popular preference for Kelsey and its variants may be influenced by names like Chelsea and Casey.