To go kerflooey is to fail or go wrong, sometimes in a spectacular way. From a glitching laptop to a car that leaves you stranded in the middle of the road, we've all had moments when things went kerflooey.
The word kerflooey doesn't have a formal root, but its meaning is written right into its sound: It belongs to a family of nonsense slang words — like blooey or flooey — that mimic the noise of something breaking down. The ker- "prefix" is a classic linguistic trick used in onomatopoeia (think kerplunk or kersplat) to add emphasis to the sound of an impact. It gives flooey that little extra punch, helping kerflooey capture the chaotic energy of things falling apart.