Where does it come from

The 6-3-5 Brainwriting method is the best known variant of brainwriting. Brainwriting is the formation of ideas in a group, and unlike brainstorming, which is perhaps the most well-known creative approach, finding ideas is done in writing and hence nonverbally.

Bernd Rohrbach, a German management consultant, created the 6-3-5 Brainwriting method, also known as the 635 method, method 635, or 6-3-5 method or 635 for short, and published it in the sales magazine Absatzwirtschaft in 1968.