The story
The earliest written reference to the town is in the Anglo-Saxon Chronicle, where it is spelled "Rumcofan", literally meaning "a wide cove or bay". This word is derived from the Old English words rúm (“wide, broad”) and cofa (“cave, cove”). Other historical spellings of Runcorn include "Rumcoven", "Ronchestorn", "Runckhorne", and "Runcorne".
Etymology from Wiktionary, CC BY-SA 4.0.