The name Ĳssel (older Isla, Isala, from *Īsalō), is thought to derive from a Proto-Indo-European root *eis- "to move quickly" (Old Norse eisa "to race forward", Latin ira "anger").
Before the early Middle Ages, the Zuiderzee had not yet formed, and in its place there was an inland lake known as Vlies (Lat.
Flevo), and the IJssel flowed through the surrounding lakelands.
However, since the formation of the Zuiderzee and obstruction from the Afsluitdijk, the IJssel no longer flows into its estuary, the Vlie, now restricted in meaning and referring only to the strait separating the islands of Vlieland (itself named after the Vlie strait) and Terschelling.
It is hypothesised that the now-poldered tidal inlets near Medemblik and the Ĳ (near Amsterdam) once were branches of river Ĳssel.

The river was a natural line of defence and in April 1945 had to be stormed by assault troops of the Allied armies liberating the Netherlands from the occupying forces of Nazi Germany.
Canadian histories refer to the river in English as "Ijssel".
The name Ĳssel (older Isla, Isala, from *Īsalō), is thought to derive from a Proto-Indo-European root *eis- "to move quickly" (Old Norse eisa "to race forward", Latin ira "anger"). Before the early Middle Ages, the Zuiderzee had not yet formed, and in its place there was an inland lake known as Vlies (Lat. Flevo), and the IJssel flowed through the surrounding lakelands. However, since the formation of the Zuiderzee and obstruction from the Afsluitdijk, the IJssel no longer flows into its estuary, the Vlie, now restricted in meaning and referring only to the strait separating the islands of Vlieland (itself named after the Vlie strait) and Terschelling. It is hypothesised that the now-poldered tidal inlets near Medemblik and the Ĳ (near Amsterdam) once were branches of river Ĳssel.
The river was a natural line of defence and in April 1945 had to be stormed by assault troops of the Allied armies liberating the Netherlands from the occupying forces of Nazi Germany. Canadian histories refer to the river in English as "Ijssel".
IJssel