I learned about this from [[Satpal Singh]] JapJi Sahib kathaa (spelled slightly differently in [[18 - ਅਸੰਖ ਮੂਰਖ ਅੰਧ ਘੋਰ ॥|Pauree 18 of Jap Ji Sahib]]). It is a great addition to [[My personal Gurbani dictionary]]. ਅੰਧ ਕੂਪ is like a deep, dark, pit. Imagine being inside a cave deep inside the earth. Total blackout darkness. This is metaphor for those who are totally blind to Vaheguru.