The concept of 'radicalization' is now used to account for all forms of violent and non-violent political Islam. Used widely within the security services and picked up by academia, the term was initially coined by the General Intelligence and Security Service of the Netherlands (AIVD) after the 9/11 and Pentagon attacks, an origin that is rarely recognized. This presentation will trace the rise and origin of this concept, as it emerged in relationship to the growing politicization of Muslim communities in the low countries. The presentation will center on the case of the Netherlands and Belgium.