The name originally approved in 1870 for this street was Cosgrove Street. It seems likely that it is connected with a pharmacist named W. Cosgrove, resident at Greenmount in 1877, or another member of his family. He is recorded as "Cosgrove, W., druggist (of Cosgrove & Co.)" (BPU, 1877). However, by 1872 the name was recorded as Cosgrave Street in council minutes and this is the spelling which stuck in the long run. Cosgrove and Cosgrave are two different anglicisations of the same Irish surname and they are frequently confused. The exact reason for the change in spelling in this case is unclear, but if it began as an administrative error, it is possible that it was not corrected later because Greenmount had been demolished and W. Cosgrove had moved away from the neighbourhood. This is suggested by the fact that Greenmount is no longer recorded as a house on North Queen Street by 1880 (BPU).