The originators of the programme, Julia Smith and Tony Holland came up with the name Walford. Tony was keen for the name to sound like Walthamstow, because of family connections. So they combined "Wal" with the suffix "ford" which is found throughout Essex.
How about the number of the borough?
The East End boroughs go in alphabetical order from 1 to 18. East 19 sounded clumsy, and so East 20 was chosen because it had a more rounded feeling to it.
Do the street names have any significance?
During their early research, the programme makers read that the East End had once been the haunt of notorious highwaymen, including Dick Turpin. So they chose "Turpin Road".
The fictional Albert Square was built in the time of Queen Victoria, and so it was named after her husband. "Bridge Street" was chosen because it connects the Square to the market. "Daisy Lane" near the police station was named after Steven Keogh's daughter (Series Designer). "George Street" has no particular significance.