The story
From mind + numbing. Compare Old English ġemynd-benimming (“lethargy”, noun, literally “numbing of the mind, mind-numbing”).
Etymology from Wiktionary, CC BY-SA 4.0.
mind-numbing
Today it means: Excessively boring, tedious, or dull; repetitive; of an activity, etc., lacking any interest or variety that might serve as intellectual stimulation. Full definition →