'Ilford' means the ford over the Hyle, an old name of the River Roding.
It is first recorded in the Domesday Book of 1086 as Ilefort, though that entry refers to Little Ilford, across the river. The Hyle, from an old Celtic word meaning 'trickling stream', was the ancient name of the lower Roding. To tell the two places apart, the town was long called Great Ilford.