Probably named after Porthallow, a fishing village on the east coast of the Lizard Peninsula, Cornwall. Historical forms include Portalla (1296), Porthalla (1302). The street name appears for the first time in the 1890 Belfast And Province Of Ulster Directory.
In 1882 the name Portobello Street was approved for part of a development between Cregagh Road and Castlereagh Road. It is likely that this was replaced by Portallo Street. This is the P in an alphabetical sequence of streets built in the 1880s and 1890s.