From the web
Kirby is derived from the Old German kirkja byr, which means “settlement by a church,” or “from the church village.” The English form means “church farm,” the Norse form “from the church farm,” or “from the church village,” the Anglo Saxon form “church town,” and the Scandinavian form “village with the church.” In Irish, Kirby means “surname.”
It's from the Scandinavian "Kirk" for church, There are a number of places with Kirkby prefix, Lonsdale, Stephen, Malham, moorside to name a few
KIRK, KIRK- and KIR- The English 'church' became Scandinavian 'kirk' in The Danelaw and is found both as a prefix and a suffix in place-names. In some instances, the second 'k' has been lost from the spelling over the years.