Gets it name from "Castleton" the residence of the Thompson family. The castellated residence named "Castleton" was erected to take the place of an earlier residence named Jennymount. In an account of a demonstration, April 15, I848, the residence is called "Castlemount". (John J. Marshall, Origin of Some of Belfast's Street-Names, p. 6)
"That on the application of Mr. A. Crawford, on behalf of the owners of property, the two new streets off York Road, near the Grove property, be named Alexandra Park Avenue and Castleton Avenue respectively, as defined in Mr. Campbell’s letter, subject to the approval of the Council". (21st January 1891)