The term "Fuzzy Front End" (FFE) was coined by Reinertsen in his 1985 article blitzkrieg-product-development in Electronic Business Magazine, written while he was at McKinsey & Co. It describes the ambiguous, poorly-defined early phase of product development — before a project has clear requirements, committed resources, or a formal project plan. The FFE is characterized by high uncertainty and low information, making it the phase where traditional project management tools (Gantt charts, detailed planning) are least effective.
The concept became widely adopted across the product development field, far beyond Reinertsen's own work. It connects to his broader argument about managing-variability — the FFE is where variability is highest and where the economic-framework-for-prioritization matters most, because decisions made in this phase have the highest leverage on total project economics. The cost-of-delay of getting the FFE wrong compounds through the entire development cycle.
While the term became standard industry vocabulary, Reinertsen's deeper point — that the FFE requires economic decision-making under uncertainty, not detailed planning — is often lost when organizations try to "tame" the front end through more process rather than better economics.