Built just after WWII. Streets named after Scottish rivers and the suffix Muir which means either Moor or Sea and Avon itself meaning River. There are a few rivers called the Avon in the UK but this street name probably refers to the Avon in Falkirk at a guess. The river is 31km long, has its source near Cumbernauld and flows into the Firth of Forth near Grangemouth.
In Pengam, probably built late 1920s. But where does the name come from? Some say surrounding streets were named after airmen, councillors or those employed by Lord Tredegar, but Bronwydd meaning wooded hillside seems out of place here.
The connection between the names of these streets Mervyn, Meredith, Madoc appears to be that they are all Welsh Princes. Merfyn ap Rhodri (died c. 900) was a late 9th-century Aberffraw prince of Gwynedd.