The time when you don't fully understand something, but try to explain it to someone else, and you're bullshitting the whole thing and realize what you're actually saying and understand what you're trying to say

A phrase to describe someone who is cognitively degenerating. Synonym of "going off the deep end". Can have varying degrees of severity.

Reference to the song "Hey You" by Pink Floyd. The line "and the worms ate into his brain" makes no sense in an otherwise linear and literal narration throughout the lyrics.