The brook may originally have been named Scirbrunan in old English which translates as "shirebourn" meaning "county stream". The name Shirebourne appears in the Barnet Manor Rolls in 1277 and the upperreaches of the Shirebourne in the modern King George's Fields were known in 1556 as Sheredyche. The manor rolls for 1699mention a field known as Sherborne Meadow and the index to the 1817 enclosure map mentions Sherbourn Field abutting the Shirebourne. The brook may be the one that formed the county boundary between Hertfordshire and Middlesex.