dunder

noun3

1. •
   (informal) A double underscore, __.

   • Python has a dunder method, __iter__, that defines what the behavior is for looping over an instance. — 2012
2. •
   (Caribbean) The lees or dregs of cane juice, used in the distillation of rum.

   • The use of dunder in the making of rum, answers the purpose of yeast in the fermentation of flour. — 1793
3. •
   (Australia) Distillery effluent.