Pain Poolish – a yeast starter preferably made with fresh yeast, aka known as mother dough

The common, but undocumented, origin given for the term poolish is that it was first used by Polish bakers around 1840, hence its name, and as a method was brought to France in the beginning of the 1920s. 

A pre-ferment in the bread-making process has several benefits: there is more time for yeast, enzyme and, if sourdough, bacterial actions on the starch and proteins in the dough; this in turn improves the keeping time of the baked bread, and it creates greater complexities of flavor.