A whole taken apart into its parts, and a failure of something that was holding. The same word for analysis and for collapse.
Compound of break (Old English brecan) and down (from Old English of dune, off the hill); the analytical sense and the collapse sense both grow from the same image of something coming apart.
One word for taking a whole apart to understand it and for a whole failing on its own — analysis and collapse, told in the same breath.