Ailsa \a(i)-lsa, ail-sa\ as a girl's name is of Old Norse origin, and the meaning of Ailsa is "island of Alfsigr". Place name: the tiny Scottish rocky islet Ailsa Craig in the estuary of the river Clyde. Alfsigr is a personal name meaning "elf or magical victory". Use as a given name has been influenced by Ealasaid, the Gaelic form of Elizabeth (Hebrew) "God's promise". The name may also be used as a homonym for Elsa".